' 


.REESE  LIBRARY 


_-n_ji_n, 


UNIVERSITY  OF  CALIFORNIA. 

Deceive  J         &£&&*<  ,189(0. 

No  .(od  I 2^5  •     QiUs  No. 


m-^' 


•I 


LABORATORY    MANUAL 


INORGANIC  PREPARATIONS 


H.  T.  VULTE,  PH.  D .,  F.  C.  S. 

•K01-KSSOK    OF    CHKMISTKY    IN     BAKNAKO     COLLEGE,    AND    ASSISTANT    IN    CHEMISTRY    AT    THE 
SCHOOL    OK    MINES,    COLUMBIA    COLLEGE,    N.    Y. 

AND 

GEORGE  M.  S.  NEUSTADT 


OF'THF- 

tTNIVERSIT  Y 

OF 


NEW    YORK 
GEO.    C.OTTSBERGER    PECK,  PUBLISHER 

II    MURRAY    STREET 


1895 


^ 


Entered,  according  to  Act  of  Congress,  in  the  year  1895, 

BY  GEO.  GOTTSBERGER  PECK, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C- 


PREFACE.- 


The  study  of  inorganic  chemistry  naturally  precedes  that  of 
organic,  and  in  a  certain  way  this  plan  is  carried  out  in  a  com- 
plete chemical  course.  The  study  of  the  organic  branch,  how- 
ever, proceeds  on  a  much  more  logical  plan  than  that  usually 
adopted  in  inorganic  work;  one  of  the  chief  advantages  being 
the  practical  work,  to  which  the  student  is  introduced  very 
early  in  his  course.  The  following  work  is  synthetic,  and  shows 
how  compounds,  often  very  complex  in  character,  rare  in  occur- 
rence or  expensive  in  preparation,  may  be  produced  from  simple 
substances,  or  from  those  which  are  comparatively  plenty  and 
cheap,  and  at  the  same  time  the  bye  products  may  be  saved. 
Such  a  course  of  study  is  of  great  value  in  inorganic  work,  but 
should  precede  and  lead  up  to,  and  not  follow  organic  chem- 
istry. However,  a  contrary  plan  seems  to  have  been  followed, 
for  while  we  have  various  works  on  organic  preparations,  there 
are  none,  so  far  as  the  authors  know,  in  the  inorganic  branch 
of  the  subject  (at  least  not  in  English),  excepting  the  works  on 
Elementary  Chemistry  ;  and  where  these  treat  of  the  subject  in 
laboratory  practice,  the  methods  are  those  which  cannot  be 
recommended  as  the  best  and  most  economical. 

In  many  laboratories  the  waste  of  material  is  greater  than  the 
use.  Students  are  apt  to  acquire  the  idea  that  after  a  certain  re- 
sult has  been  produced  the  rest  of  the  material  is  worthless,  and 
in  consequence  much  loss  occurs  from  throwing  away  valuable 
substances,  which  can  be  recovered  or  used  with  little  trouble  or 
expense.  It  is  not  a  very  difficult  operation  to  purify  the  various 
commercial  salts,  converting  them  into  C.  P.  reagents,  and  in  the 
operation  the  student  cannot  help  acquiring  facts  which  are 
directly  and  forcibly  brought  to  his  knowledge.  Too  much  reli- 
ance is  usually  placed  on  the  so-called  C.  P.  chemicals  in  com- 
mon use.  Many  are  high-priced  and  apt  to  deteriorate  in  the 


11  PREFACE. 

packages.  There  is  no  reason  why  the  student  should  not  pre- 
pare many  of  these,  unless  it  be  that  he  does  not  always  know 
where  to  look  for  the  necessary  information. 

The  book  is  designed  to  meet  a  long  felt  want  in  the  inor- 
ganic laboratory,  in  training  the  student  to  prepare  his  own 
reagents  and  to  test  them  for  the  customary  impurities.  The 
methods  are  largely  those  in  commercial  use,  and  should  prove 
of  value  to  those  studying  Applied  Chemistry. 

The  works  of  Fresenius,  Erdmann  and  others,  as  well  as  the 
various  chemical  journals  for  some  years  past,  have  been  carefully 
searched,  and  such  information  as  \vas  thought  valuable  has  been 
collected  and  arranged  in  order,  beginning  with  the  simplest 
operations  and  gradually  increasing  in  difficulty  as  the  student 
acquires  skill  in  his  work.  As  far  as  possible,  references  to  the 
original  articles  have  been  given. 

OCTOBER,  1895. 


LABORATORY  MANUAL 


OF 


INORGANIC    PREPARATIONS, 


WATER. 
H2O. 

Pure  water  is  obtained  by  distilling  spring  water  from 
a  copper  still  with  head  and  condenser  made  of  pure 
tin.  The  distillation  is  carried  to  about  three-fourths 
of  the  quantity  operated  upon.  If  it  is  desired  to  have  the 
distilled  water  perfectly  free  Irom  carbonic  acid  and  am- 
monium carbonate,  the  portions  passing  over  first  must  be 
rejected.  In  the  larger  chemical  laboratories,  distilled 
water  is  obtained  from  the  steam  apparatus  which  serves 
for  drying,  etc.  Rain  water  collected  in  the  open  air  may 
in  many  cases  be  substituted  for  distilled  water. 

It  must  be  colorless,  odorless,  and  tasteless,  and 
should  not  leave  the  smallest  residue  when  evaporated  in  a 
platinum  vessel.  It  should  not  be  changed  by  ammonium 
sulphide  (copper,  lead,  iron),  nor  rendered  turbid  by  baryta 
water  (carbonic  acid).  No  cloudiness  should  be  caused 
even  after  long  standing  by  the  addition  of  ammonium 
oxalate,  of  barium  chloride  and  hydrochloric  acid  (sul- 


2  LABORATORY    MANUAL    OF 

phuric  acid),  of  silver  nitrate  and  nitric  acid  (chlorides),  or 
of  mercuric  chloride  and  sodium  carbonate  (ammonia). 

We  use  water  principally  as  a  simple  solvent  for  a  great 
variety  of  substances. 

AMMONIUM— FREE  WATER. 

If  the  ordinary  distilled  water  gives  a  reaction  for  am- 
monia with  Nessler's  reagent,  it  should  be  treated  with 
sodium  carbonate,  about  one  gram  to  the  litre  and  boiled 
until  one-fourth  has  been  evaporated. 

Ammonium  free  water  may  also  be  prepared  by  dis- 
tilling water  made  slightly  acid  with  sulphuric  acid. 

WATER  FREE  FROM  ORGANIC  MATTER  AND  AMMONIA.* 

About  15-20  litres  of  ordinary  distilled  water,  to  which 
about  I  gram,  of  potassium  hydrate  and  0.2  gram,  of 
potassium  permanganate  have  been  added  are  maintained 
at  about  100°  C.  for  twenty-four  hours  under  an- inverted 
condenser,  after  which  the  condenser  is  reversed  and  the 
water  distilled  off.  Apply  Nessler's  test  to  the  distillate 
from  time  to  time,  until  100  c.c,  show  no  coloration  and 
collect  that  which  comes  over  subsequently,  stopping 
5OOC.C.  short  of  dryness. 

As  an  additional  precaution  the  water  thus  obtained 
may  be  acidified  with  sulphuric  acid  and  re-distilled. 

For  preparing  distilled  water,  the  ordinary  tin  lined 
copper  still  and  block  tin  condenser  may  be  used,  or  a 
more  economical  way  is  to  make  use  of  the  well  known 
Domestic  Water  Still,  (Fig.  i).  This  piece  of  apparatus 

*  Water  Analysis,  FRANKLAND,  p.  113. 


INORGANIC   PREPARATIONS.  3 

yields  a  good  quality  of  product,  with  a  minimum  ex- 
penditure of  heat  and  condenser  water,  and  is  moreover 
very  compact. 


FIG.  l. 

Water  free  from  organic  matter  and  ammonium,  which 
is  indispensable  in  water  analysis  and  the  preparation  of 
many  standard  solutions  such  as  potassium  permanganate, 
argentic  nitrate  etc.,  is  best  prepared  in  the  apparatus 
shown  in.  Fig  2,  which  consists  of  a  glass-stoppered  flask 
with  side-neck  tube.  The  end  of  the  side-neck  tube  is  turned 
vertically  downward,  being  thrust  deeply  into  the  tin  tube 
of  the  condenser,  and  held  in  place  there  by  a  short  piece  of 
rubber  tubing.  The  three-eighth  inch  block  tin  pipe  forming 
the  condenser-tube  is  bent  zigzag  instead  of  in  the  conven- 


LABORATORY    MANUAL    OF 


tional  helix.  This  affords  a  more  even  flow  of  the  distillate. 
The  cylindrical  copper  jacket  containing  the  water  for  cool- 
ing is  about  four  inches  in  diameter,  and  fifteen  inches  long. 
The  disk  closing  the  lower  end  is  arched  upward  so  that  in 


FIG.  2. 


case  the  condenser  "  sweats  "  from  the  use  of  very  cold 
water,  the  drip  from  the  outside  can  not  contaminate  the 
distillate.  The  lower  end  of  the  tin  tube  is  cut  aslant  for 
the  more  certain  delivery  of  the  distillate. 


INORGANIC   PREPARATIONS.  5 

/X^SErUB^> 

(UNIVERSITY; 

Vc^?w.V 

ETHYL     ALCOHOL. 
C2H5.OH. 

Two  sorts  of  alcohol  are  used  in  chemical  analy- 
sis, viz. :  1st,  Commercial  "  95  per  cent,  alcohol," 
which  really  contains  93  to  94  per  cent,  of  alcohol 
by  weight ;  and  2d,  absolute  alcohol.  The  latter  may  be 
prepared  most  conveniently  by  placing  in  a  flask  or  tin  can 
800  grams  of  good  quick-lime  in  coarse  powder  or  small 
lumps,  adding  I  litre  of  "  95  per  cent,  alcohol,"  connecting 
the  vessel  with  the  lower  end  of  a  Liebig  condenser,  and 
keeping  its  contents  boiling  on  a  water  bath  for  an  hour. 
The  can  is  then  connected  to  the  upper  end  of  the  conden- 
ser, and  the  dehydrated  alcohol  distilled  off  into  a  bottle 
for  use.* 

Pure  alcohol  must  completely  volatilize,  and  ought 
not  to  leave  a  smell  of  fusel-oil  when  rubbed  between 
the  hands ;  nor  should  it  alter  the  color  of  moist  blue  or 
red  litmus  paper.  When  kindled,  it  must  burn  with  a  faint 
bluish,  barely  preceptible  flame. 

Commercial  Alcohol  invariably  contains  aldehyde  and 
if  kept  in  tin  cans  stannic  oxide  as  well;  such  alcohol  can- 
not be  used  for  the  preparation  of  alcoholic  potash  solutions, 
argentic  nitrate  or  for  Hiibl's  iodo-mercuric  chloride 
solution.  For  such  purposes  either  of  the  two  following 
methods  may  be  used. 

A  convenient  amount  of  the  alcohol  to  be  purified  is 
shaken  with  pulverized  potassium  permanganate  until  it 
a'ssumes  a  decided  color.  It  is  then  allowed  to  stand  for 


*  ERLENMEYER  ;  J.  LAWRENCE  SMITH. 


6  LABORATORY    MANUAL   OF 

some  hours,  until  the  permanganate  has  been  decomposed 
and  brown  manganese  oxide  is  deposited.  A  pinch  of 
pulverized  calcium  carbonate  is  then  added,  and  the  alcohol 
distilled  at  the  rate  of  about  50  c.  c.  in  20  minutes  from 
a  flask  provided  with  a  Wurtz  tube  or  one  of  the  Lebel- 
Heninger  pattern.  The  distillate  is  tested  frequently  until 
about  10  c.  c.  thereof,  when  boiled  with  I  c.  c.  of  strong 
(syrup)  solution  of  caustic  soda  or  potash,  gives  no  percept- 
ible yellow  coloration  on  standing  for  20  minutes  or  half 
an  hour.  What  distills  over  after  that  time  is  preserved  for 
use. 

The  first  distillates  may  be  added  to  the  small  amount 
remaining  in  the  distilling  flask  (which  should  not  be  driven 
down  to  the  complete  dryness),  and  a  fresh  portion  of  puri- 
fied alcohol  recovered. 

The  rationale  of  the  proceeding  appears  to  be  that  the 
permanganate  oxidizes  and  destroys  chiefly  the  fusel-oil, 
furfurol  and  other  compounds  of  that,  nature,  the  acids 
resulting  from  the  reaction  are  neutralized  by  the  calcium 
carbonate  added  before  distillation,  and  by  distilling 
slowly  the  aldehyde  at  least  is  concentrated  in  the  first 
portions  of  the  distillate.  Distillation  of  alcohol  contain- 
ing caustic  potash  or  soda  seemed  to  cause  a  constant 
formation  of  aldehyde.  The  alcohol  thus  purified  is  per- 
fectly neutral,  and  gives  most  satisfactory  results  when 
used  as  a  solvent  for  caustic  alkalies  or  silver  nitrate,  the 
solutions  remaining  as  colorless  as  distilled  water,  even 
after  boiling  and  standing  indefinitely,  if  properly  pro- 
tected from  dust  and  other  external  influences.* 


*  Jour.  Am.  Chem.  Soc. — E.  WALLER. 


INORGANIC    PREPARATIONS. 


The  second  method  consists  in  distilling  the  alcohol 
with  some  caustic  potash  in  the  presence  of  a  large  quantity 
of  non-volatile  fatty  acid  ;  either  oleic  or  stearic  is  gener- 
ally used,  the  process  is  simple  and  the  result  good. 


OXYGEN. 
O. 

The  compressed  gas  put  up  in  steel  cylinders  is 
sufficiently  pure  for  most  purposes,  but  when  not  avail- 
able the  gas  may  be  readily  prepared  by  heating  a  mixture 
of  equal  parts  of  potassium  chlorate  and  manganese  di- 
oxide, in  a  copper  retort,  or  better,  in  an  apparatus  similar 
to  fig.  3. 


FIG.  3. 

Oxygen  gas  made  in  this  way  is  liable  to  contain 
chlorine  or  oxides  of  chlorine  and  carbon  dioxide,  it  is 
purified  by  washing  with  potassium  hydrate  and  dried  by 
passing  through  concentrated  sulphuric  acid. 

Oxygen  may  also  be  prepared  by  treating  sodium 
dioxide  NagOg  with  dilute  acid,  either  hydrochloric  or 
sulphuric. 


8  LABORATORY    MANUAL    OF 

Na2O2  +  2H.C1  =  O  +  2NaCl  +  H3O, 

great  heat  is  evolved  in  this  reaction  and  the  operation 
must  be  conducted  with  care;  it  is  however  an  excellent  way 
to  oxidize  solutions,  in  which  case  the  solution  is  made  acid 
and  the  sodium  dioxide  dropped  in  and  well  stirred  until 
the  desired  effect  has  been  produced. 

In  the  wet  way  oxygen  is  produced  by  treating 
"Chloride  of  Lime  "  Ca(ClO)2,CaCl3  in  disc  form,  in  a  Kipp's 
Apparatus  with  a  mixture  of  I  litre  of  hydrogen  dioxide  and 
53  c.  c.  nitric  acid  com.  Sp.  Gr.  1.265.  The  same  pre- 
cautions for  purification  are  necessary  as  in  the  case  of 
manganese  dioxide  and  potassium  chlorate. 

To  prepare  oxygen,  cubes  consisting  of  a  mixture  of 
2  parts  of  barium  dioxide,  I  part  of  manganese  dioxide 
and  i  part  of  pla.ster  are  used  with  hydrochloric  acid  (sp. 
gr.  1.12)  diluted  with  an  equal  volume  of  water.  The  oxy- 
gen evolved  contains  traces  of  chlorine  and  must  there- 
fore be  washed  with  an  alkali.* 

It  can  also  be  prepared  by  adding  potassium  perman- 
ganate to  hydrogen  peroxide  made  alkaline  with  ammonia.t 

Oxygen  is  a  colorless  gas,  and  without  odor.  It  is 
liquified  with  difficulty,  requiring  a  pressure  of  320  atmos- 
pheres at  212°  F.  Oxygen  is  remarkable  for  the  wide 
range  of  its  chemical  attraction  for  other  elementary  bodies 
with  all  of  which  it  is  capable  of  entering  into  combi- 
nation except  one,  namely  fluorine. 


*  G.  NEUMANN,  Ber.  20,  1584. 

f  C.  F.  GOHRING,  Chem.  Zeit.  12,  1659. 


INORGANIC    PREPARATIONS. 


HYDROGEN. 
H. 

Hydrogen  is  best  prepared  from  granulated  zinc 
and  dilute  sulphuric  acid  (i  litre  acid,  5  litres  water)  in 
Kipp's  Apparatus ;  the  zinc  should  not  be  too  pure  or  the 
supply  of  gas  will  be  slow  and  feeble.  In  any  case  it  is  well 
to  add  a  small  amount  of  copper  sulphate  solution,  just 
sufficient  to  produce  a  thin  coat  of  copper  on  the  zinc,  01 
a  piece  of  platinum  foil  may  be  used  in  place  of  the  copper 
sulphate ;  in  this  latter  case  it  is  better  to  amalgamate  the 
zinc,  by  first  treating  with  dilute  sulphuric  acid  and  then 
adding  mercury  and  shaking,  or  by  simply  treating  the 
zinc  with  a  strong  solution  of  mercuric  nitrate  containing 
free  nitric  acid. 

A  granulated  alloy  of  tin  and  zinc,  containing  about  83 
per  cent,  of  the  latter,  prepared  by  adding  zinc  to  molten 
tin  as  long  as  it  dissolves,  is  recommended  for  use  in 
Kipp's  apparatus.  The  pieces  retain  their  shape  and  size 
after  all  the  zinc  is  dissolved  out,  and  therefore  have  no 
tendency  to  fall  through  into  the  lower  bulb.* 

Hydrogen  may  also  be  prepared  by  sodium  amalgam 
with  dilute  acids. 

Hydrogen  gas  prepared  by  the  action  of  zinc  and  acid 
is  never  pure,  but  may  contain  hydrocarbons,  hydrogen 
sulphide,  sulphur  dioxide,  etc. 

The  very  small  amount  of  arsenic  generally  present, 
as  AsH3,  may  be  neglected.  The  other  impurities  are  re- 
moved by  first  passing  the  gas  through  a  solution  of 


*  J.  HABERMANN,  Zeit.  Anal.  Chem.  28, 

(tri 

- 


ID  LABORATORY    MANUAL    OF 

potassium  permanganate  in  order  to  oxidize  hydrocarbons, 
hydrogen  sulphide,  etc.,  then  through  the  potassium 
hydrate  to  absorb  carbon  dioxide,  sulphur  dioxide,  etc., 
and  finally  through  concentrated  sulphuric  acid  and  calcium 
chloride  to  remove  water. 

Hydrogen  is  a  colorless,  odorless  and  tasteless  gas,  is 
highly  combustible,  burning  with  a  very  hot  but  slightly 
luminous  flame,  and  when  mixed  with  air  or  free  oxygen, 
explodes  with  violence. 


NITROGEN. 

N. 

This  gas  is  seldom  used,  but  when  required  may  be 
readily  prepared  by  heating  equal  parts  of  concentrated 
aqueous  solutions  of  ammonium  chloride  and  potassium  or 
sodium  nitrite. 

NH4  Cl  +  KNO2  =  N3  +  KC1  +  2H2O. 

The  operation  is  conducted  in  a  roomy  flask,  the  out- 
going gas  mixed  with  steam,  ammonium  chloride,  and  pos- 
sibly some  oxides  of  nitrogen,  is  cooled  washed  with  water 
and  dried  over  sulphuric  acid.  Nitrogen  prepared  in  this 
way  contains  no  argon. 

Nitrogen  is  a  colorless,  odorless  and  tasteless  gas,  and 
is  a  non-supporter  of  combustion. 


CHLORINE  AND  CHLORINE  WATER. 

Cl. 

Chlorine  is  prepared  by  mixing   18  parts  of  common 
salt  in  lumps  with  1 5  parts  of  finely  pulverized  good  man- 


INORGANIC    PREPARATIONS.  II 

ganese  dioxide,  free  from  calcium  carbonate ;  put  the  mix- 
ture in  a  flask,  pour  a  completely  cooled  mixture  of  45  parts 
of  concentrated  sulphuric  acid  and  2 1  parts  of  water  upon 
it,  and  shake  the  flask  :  a  uniform  and  continuous  evolution 
of  chlorine  gas  will  soon  begin,  which,  when  slackening 
may  be  easily  increased  again  by  the  application  of  a  gentle 
heat.  This  method  of  WlGGERS  is  excellent,  and  can  be 
highly  recommended.  Conduct  the  chlorine  gas  evolved 
first  through  a  flask  containing  a  little  water,  then  into  a 
bottle  filled  with  cold  water,  and  continue  the  process  until 
the  fluid  is  saturated.  Where  it  is  desired  to  obtain 
chlorine  water  quite  free  from  bromine,  the  washing  flask 
is  changed  after  about  one-half  of  the  chlorine  has  been 
expelled,  and  the  gas  which  now  passes  over  is  conducted 
into  a  fresh  bottle  filled  with  water.  If  the  chlorine  water 
is  to  be  quite  free  from  hydrochloric  acid,  the  gas  must  be 
passed  through  a  U  tube  containing  manganese  dioxide. 
The  chlorine  water  must  be  protected  from  the  action  of 
light ;  since,  if  this  precaution  is  neglected,  it  speedily  suf- 
fers complete  decomposition,  being  converted  into  dilute 
hydrochloric  acid,  with  evolution  of  oxygen  (resulting  from 
the  decomposition  of  water).  Smaller  quantities,  intended 
for  use  in  the  laboratory,  are  best  kept  in  a  stoppered 
bottle  protected  by  a  case  of  pasteboard.  Chlorine  water 
which  has  lost  its  strong  peculiar  odor  is  unfit  for  use. 

CHLORINE  FROM  CHLORIDE  OF  LIME  IN  KIPP'S  APPA- 
RATUS. 

Dry  chloride  of  lime  is  intimately  mixed  with  plaster 
and  moistened  to  such  a  degree  that  it  can  only  with  diffi- 
culty be  rolled  into  balls  between  the  fingers.  It  is  made 


12  LABORATORY    MANUAL   OF 

homogeneous  by  powdering  in  an  iron  mortar  and  beaten 
into  an  iron  frame  10-12  m.m.  high  by  means  of  an  iron 
mallet.  It  is  then  covered  with  a  piece  of  oilcloth  and 
submitted  to  great  pressure.  The  plate  of  chloride  of  lime 
is  then  cut  into  cubes  while  still  in  the  frame  and  dried  as 
quickly  as  possible  at  20°  C.  The  cubes  are  then  preserved 
in  well-closed  vessels.  It  is  used  in  a  Kipp's  apparatus 
with  hydrochloric  acid  (sp.  gr.  1.124)  diluted  with  an 
equal  volume  of  water.  The  acid  must  be  free  from  sul- 
phuric acid.* 

When  chlorine  is  generated  from  bleaching  powder  and 
hydrochloric  acid  in  a  Kipp's  apparatus,  it  is  advisable,  af- 
ter using  the  apparatus,  to  blow  in  a  little  air,  otherwise  a 
slow  but  continuous  action  takes  place,  owing  to  the  ab- 
sorption of  the  chlorine  by  the  acid.t 

APPARATUS  FOR  A  CONSTANT  SUPPLY  OF  CHLORINE. 

I.  The  manganese  dioxide  is  used  in  fragments  the  size  of 
peas,  and  is  placed  in  a  two-necked  bottle,  at  the  bottom 
of  which  there  is  a  layer  of  broken  glass  or  pumice.  This 
stands  in  a  water  bath.  Hydrochloric  acid  is  supplied 
from  a  reservoir  at  a  higher  level  by  a  tube  reaching  to 
the  bottom  of  the  layer  of  glass,  a  T-piece  and  stopcocks 
allowing  the  same  tube  to  serve  for  the  removal  of  the 
manganese  solution.  The  corks  should  be  soaked  in  par- 
affin. Suitable  drying  apparatus  can  be  attached  and  will 
not  require  replenishing  for  a  long  time.  The  chlorine 
begins  to  come  off  when  the  temperature  of  the  bath 
reaches  50°  C.,  and  by  means  of  a  stopcock  on  the  outlet  its 


*  C.  WINKLER,  Ber.  20,  184. 
f  C.  WINKLER,  Ber.  22,  1076. 


INORGANIC    PREPARATIONS.  13 

rate  is  completely  under  control.  The  evolution  can 
speedily  be  arrested  by  closing  the  stopcock  at  the  outlet 
of  the  drying  apparatus  and  emptying  the  water  bath. 

The  apparatus  is  then  left  full  of  chlorine,  and  is  ready 
at  any  moment  to  give  supply  of  the  gas  completely  free 
from  oxygen.* 

II.  From   sodium   chloride,   pyrolusite,   and   sulphuric 
acid. — It  is  usually  supposed  that  in  this  reaction  the  whole 
of  the  chlorine  is  evolved  in  the  free  state ;  detailed  experi- 
ments have,  however,  shown  that  this  is  not  the  case,  but 
that  the  reaction  which  takes  place  is  as  follows : 

4NaCl+  MnO3  +  3H3SO4  =  2NaHSO4  f  Na3SO4  +  MnCl3+ 
2H3O  +  C12. 

The  necessary  proportions  are,  therefore,  5  parts  of 
pyrolusite,  11  parts  salt,  and  14  parts  of  sulphuric  acid 
diluted  with  an  equal  volume  of  water. 

III.  From  pyrolusite,  hydrochloric  and  sulphuric  acids. 
— The  instructions  usually   given  for   the  preparation   of 
chlorine  by  this  method  are  to  take  I  part  of  pyrolusite,  2 
of  hydrochloric  acid  of  sp.  gr.  1.14,  and  I  part  of  sulphuric 
acid  mixed  with  an  equal  bulk  of  water,  the  reaction  being 
supposed  to  take  place  according  to  the  equation : 

MnO3+  2HC1  +  H3SO4  =  MnSO4  +  2H3O  +  C13. 

As  in  the  foregoing  case  this  equation  is  quite  incorrect, 
only  65  per  cent,  of  the  chlorine  being  obtained  in  the  free 
state. 


*  A.  VOSMAER,  Zeit.  Anal.  Chem.,  27,  638. 


14  LABORATORY    MANUAL   OF 


CHLORINE  FOR  LABORATORY  PURPOSES. 

When  hydrochloric  acid  of  sp.  gr.  i.i,  heated  to  about 
80°  C.,  is  allowed  to  come  slowly  in  contact  with  pieces  of 
potassium  chlorate  which  have  been  previously  fused,  a 
steady  evolution  of  gas  takes  place.  Under  these  condi- 
tions, about  82  to  85  per  cent,  of  the  gas  is  chlorine,  the  re- 
mainder being  chlorine  dioxide.  Another  10  per  cent,  of 
the  dioxide  may  be  decomposed  by  passing  the  evolved 
gas  through  a  saturated  hydrochloric  acid  solution  of  man- 
ganous  chloride  at  90°  C.  If  the  gas  is  wanted  absolutely 
pure,  the  gas,  after  passing  through  the  manganous  chlor- 
ide, may  be  passed  through  a  combustion  tube  filled  with 
asbestos  and  heated  to  redness.  Care  must  be  taken  to 
have  the  acid  hot,  and  not  to  allow  the  action  to  become 
rapid,  or  the  proportion  of  chlorine  dioxide  may  become 
much  increased  and  explosion  occur,  i  gram  of  potas- 
sium chlorate  yields  about  half  a  litre  of  chlorine. 

If  a  Kipp  or  some  similar  constant  gas-generating  ap- 
paratus is  employed,  and  the  acid  heated  by  a  steam 
jacket  or  by  standing  the  generator  in  hot  water,  this 
method  forms  a  convenient  constant  chlorine  apparatus  for 
laboratory  use.* 

Chlorine  is  a  heavy  greenish,  yellowish  gas,  having  a 
strong  and  suffocating  odor,  and  if  inhaled  in  sufficient 
quantities  is  capable  of  producing  suffocation.  Free 
chlorine  gas  is  readily  detected  by  its  color  and  odor. 

*  F.  A.  GOOCH  and  D.  A.  KREIDER,  Zeit.  Anorg.  Chem.,  7,  17. 


INORGANIC    PREPARATIONS. 


HYDROCHLORIC    ACID,    OR 

HYDROGEN    CHLORIDE. 

HC1. 

Pour  a  cooled  mixture  of  seven  parts  of  concen- 
trated sulphuric  acid  and  two  parts  of  water  over 
four  parts  of  sodium  chloride  in  a  retort  ;  expose  the  re- 
tort, with  slightly  raised  neck,  to  the  heat  of  a  sand-bath 
until  the  evolution  of  gas  ceases  ;  conduct  the  evolved 
gas,  by  means  of  a  bent  tube,  into  a  flask  containing  six 
parts  of  water,  and  take  care  to  keep  this  vessel  constantly 
cool.  To  prevent  the  gas  from  receding  the  tube  ought  to 
dip  but  about  one  line  into  the  water  of  the  flask.  When 
the  operation  is  terminated,  try  the  specific  gravity  of  the 
acid  produced,  and  dilute  with  water  until  it  marks  from 
1.  1  1  to  1.12.  If  you  wish  to  ensure  the  absolute  purity  of 
the  acid,  and  its  perfect  freedom  from  every  trace  of  arsenic 
and  chlorine,  you  must  take  care  to  free  the  sulphuric  acid 
intended  to  be  used  in  the  process  from  arsenic  and  the 
oxygen  compounds  of  nitrogen,  according  to  the  directions 
(see  sulphuric  acid,  page  22.)  A  pure  acid  may  also  be 
prepared  cheaply  from  the  crude  hydrochloric  acid  of  com- 
merce by  diluting  the  latter  to  a  specific  gravity  of  1.12  and 
distilling  the  fluid  with  addition  of  some  chloride  of  sodium. 
Or  you  may  put  the  acid  into  the  retort  in  the  concentrated 
form,  placing  60  parts  of  water  into  the  receiver  for  every 
100  parts  of  concentrated  acid,  and  not  luting  the  receiver 
to  the  retort.  If  the  crude  acid  contains  chlorine  this 
should  be  removed  first  by  cautious  addition  of  solution  of 
sulphur  dioxide,  before  proceeding  to  the  distillation;  if, 


l6  LABORATORY    MANUAL    OF 

on  the  other  hand,  it  contains  sulphur  dioxide,  this  is  re- 
moved in  the  same  way  by  cautious  addition  of  some 
chlorine  water.  Hydrochloric  acid  not  unfrequently  con- 
tains arsenious  chloride,  owing  to  the  presence  of  arsenic 
in  the  sulphuric  acid  employed.  To  free  it  from  this  im- 
purity, the  acid  is  mixed  with  twice  its  volume  of  water, 
hydrogen  sulphide  is  conducted  into  it,  the  mixture  allowed 
to  stand  at  rest  for  some  time,  the  clear  fluid  then  decanted 
from  the  sulphur  and  arsenious  sulphide,  and  heated,  to  ex- 
pel the  hydrogen  sulphide. 

Hydrochloric  acid  must  be  perfectly  colorless  and 
leave  no  residue  upon  evaporation.  If  it  turns  yellow 
on  evaporation,  ferric  chloride  is  present.  It  must  not  im- 
part a  blue  tint  to  a  solution  of  potassium  iodide  mixed 
with  starch  paste  (chlorine  or  ferric  chloride),  nor  discolor 
a  fluid  made  faintly  blue  with  iodized  starch  (sulphur 
dioxide).  Barium  chloride  ought  not  to  produce  a  pre- 
cipitate in  the  highly  diluted  acid  (sulphuric  acid).  Hy- 
drogen sulphide  must  leave  the  diluted  acid  unaltered  (ar- 
senic). After  neutralization  with  ammonia,  ammonium 
sulphide  must  produce  no  change  in  it  (iron,  thallium). 

It  can  also  be  prepared  by  distilling  a  mixture  of  cone, 
sulphuric  and  hydrochloric  acids;  this  latter  method  is  bet- 
ter where  gaseous  hydrochloric  acid  is  needed. 

METHODS  FOR  OBTAINING  CONSTANT  STREAMS  OF  HY- 
DROGEN CHLORIDE  AMMONIA  AND  NITROGEN. 

Hydrogen  chloride  can  be  generated  in  a  Kipp's  ap- 
paratus by  the  action  of  ordinary  sulphuric  acid  on  carnal- 
lite  and  ammonia  gas  by  allowing  a  solution  of  ammonia 
to  react  with  solid  potassium  hydroxide.  When  the  ma- 


INORGANIC    PREPARATIONS.  I/ 

terials  are  exhausted,  the  solution  of  potash  which  is 
formed  may  be  used  for  ordinary  laboratory  purposes  after 
it  has  been  boiled  to  expel  ammonia. 

To  prepare  nitrogen  in  Kipp's  apparatus,  it  is  best  to 
employ  cubes  containing  chloride  of  lime  made  according 
to  Winkler's  method  (page  n);  these  are  treated  with 
a  mixture  of  equal  volumes  of  ammonia  and  water. 
The  resulting  gas  contains  suspended  ammonium  chloride 
and  other  impurities,  which  may  be  removed  by  passing 
it  through  water,  potash  and  sulphuric  acid.* 


FIG.  4. 

NITRIC    ACID. 

HNO3  OR  NO3OH. 

Prepared  by  slowly  distilling  a  mixture  of  5  parts  of 
sodium  nitrate  and  3  parts  of  cone,  sulphuric  acid,  in  an 
apparatus  as  shown  in  Fig.  4 ;  the  product  is  usually  not 


By  G.   NEUMANN,  (J.  pr.  Chem.  [2]  37,  342-345). 


I 8  LABORATORY    MANUAL    OF 

sufficiently  concentrated,  and  must  be  redistilled  with  five 
times  its  volume  of  cone,  sulphuric  acid  in  an  apparatus 
similiar  to  the  above.  If  the  product  is  colored  yellow  or  red 
by  dissolved  oxides  of  nitrogen,  it  may  be  rendered  color- 
less by  blowinga  current  of  dry  air  through  the  acid  for  some 
minutes.  Concentrated  nitric  acid  1.53  spcific  gravity 
has  a  strong  affinity  for  water  and  must  be  kept  closely  stop- 
pered. 

The  sudden  frothing  which  frequently  takes  place  when 
nitric  acid  is  prepared  from  sodium  nitrate  and  sulphuric 
acid  is  explained  on  the  assumption  that  the  first  portions 
pass  over  at  84°  C,  and  that  the  heating  must  be  commenced 
cautiously,  and  the  temperature  only  allowed  to  rise  after 
the  first  reaction  abates.  After  the  temperature  has  risen 
above  109°  C.,  no  acid  passes  over  until  the  temperature 
117°  C.  is  reached,  when  the  last  portions  pass  over.  The 
latter  acid  has  a  sp.  gr.  1.42,  and  corresponds  with  the 
hydrate,  2HNO3  +  H3O,  which  distills  at  120  to  121°  C. 
without  decomposition.* 

Another  method  of  preparation  is  to  heat  crude  nitric 
acid  of  commerce,  as  free  as  possible  from  chlorine,  and  of 
a  specific  gravity  of  at  least  1.31  in  a  glass  retort  to 
boiling,  with  addition  of  some  potassium  nitrate ;  let  the 
distillate  run  into  a  receiver  kept  cool,  and  try  from  time 
to  time  whether  after  dilution  it  still  continues  to  precipi- 
tate or  cloud  solution  of  silver  nitrate.  As  soon  as  this 
ceases  to  be  the  case,  change  the  receiver,  and  distill  until 
a  trifling  quantity  only  remains  in  the  retort.  Dilute  the 
distillate  with  water  until  the  specific  gravity  is  1.2. 


*  By  C.  W.  VOLNEY,  J.  Amer.  Chem.  Soc.  13,  246-251. 


INORGANIC    PREPARATIONS.  19 

Another  method  is  to  dilute  crude  nitric  acid  of  com- 
merce of  about  1.38  specific  gravity  with  two-fifths  of  its 
weight  of  water,  and  add  solution  of  silver  nitrate  as  long 
as  a  precipitate  of  silver  chloride  continues  to  form  ;  then 
add  a  further  slight  excess  of  solution  of  silver  nitrate,  let 
the  precipitate  subside,  decant  the  perfectly  clear  super- 
natant acid  into  a  retort  or  an  alembic  with  ground  head ; 
add  some  potassium  nitrate  free  from  chlorine,  and  distill 
until  only  a  small  quantity  remains,  taking  care  to  attend 
to  the  proper  cooling  of  the  fumes  distilling  over.  Dilute 
the  distillate,  if  necessary,  with  water  until  it  has  a  specific 
gravity  of  .1.2. 

Pure  nitric  acid  must  be  colorless  and  leave  no 
residue  upon  evaporation  on  platinum  foil.  Solution  of 
silver  nitrate  or  of  barium  nitrate  must  not  cause  the 
slightest  turbidity  in  it.  Dilute  the  acid  with  water  before 
adding  these  reagents,  as  otherwise  nitrates  will  pre- 
cipitate. Silver  should  be  tested  for  by  hydrochloric  acid. 


NITROUS    OXIDE. 
N2O. 

Five  parts  of  stannous  chloride,  10  parts  of  hydrochloric 
acid  sp.  gr.  1.21,  and  0.9  part  of  nitric  acid  sp.  gr.  1.38, 
are  heated  to  boiling,  when  the  evolution  of  nitrous  oxide 
commences,  and  continues  to  be  evolved  quite  regularly 
and  in  a  pure  state.  The  above  proportions  of  ingredients 
should  be  adhered  to,  as  otherwise  the  gas  is  evolved  ir- 
regularly, and  even  with  violent  explosions.* 


G.  CAMPORI,  Ann.  Chine.  Pharm.,  8,  253. 


20  LABORATORY    MANUAL   OF 

It  can  also  be  prepared  from  a  mixture  of  ammonium 
sulphate  and  sodium  nitrate,  kept  at  102°  C.  for  2  to  3  hours, 
undergoes  in  great  part  decomposition  into  sodium  sulphate 
and  ammonium  nitrate.  If,  however,  it  is  rapidly  raised 
to  a  higher  temperature,  nitrous  oxide  begins  to  be  evolved 
atiio0  C.,and  comes  off  with  some  rapidity  at  115  to  120° 
C.  During  the  heating  up  a  little  ammonia  is  evolved,  and 
the  longer  the  mixture  is  kept  at  about  104  to  1 10°  C.  the 
more  ammonia  is  lost.  If,  then,  the  two  salts  have  been  mixed 
in  molecular  proportions,  the  deficiency  in  the  ammonia 
leads  to  the  evolution  of  some  of  the  higher  oxides  of  nitro- 
gen towards  the  end  of  the  reaction.  This  may  be  remedied 
by  increasing  the  proportion  of  ammonium  sulphate,  the 
mixture,  with  an  additional  5  per  cent,  of  that  salt,  affording 
a  larger  yield  of  nitrous  oxide  than  would  be  obtained  from 
the  equivalent  quantity  of  ammonium  nitrate.  The  gas  is 
evolved  with  regularity,  whereas  ammonium  nitrate,  raised 
to  115°  C.,  decomposes  with  a  rapidity,  accelerating  towards 
explosive  violence.* 


NITRIC    OXIDE. 

NO. 

A  Woulff's  bottle,  fitted  with  a  funnel  and  delivery 
tube,  is  filled  loosely  with  strips  of  copper,  and  then  one- 
third  with  a  cold  saturated  solution  of  sodium  nitrate. 
Strong  sulphuric  acid  is  added  more  or  less  quickly,  ac- 
cording to  the  amount  of  gas  required.  The  evolution  of 
gas  is  very  regular,  and  may  be  kept  up  for  hours. f 


*  BY  W.  SMITH,  J.  Soc.  Chem.  Ind.,  11.867;  12,  10. 
f  By  H.  KAEMMERER,  Ber.   18,  3064-3066. 


INORGANIC    PREPARATIONS.  21 

Nitric  oxide  may  also  be  prepared  from  a  mixture  of 
solutions  of  potassium  ferrocyanide  and  potassium  nitrite 
added  gradually  from  a  stoppered  funnel  to  a  flask  contain- 
ing acetic  acid ;  the  contents  of  the  flask  must  be  vigor- 
ously shaken  during  the  operation.* 

Another  method  is  to  add  a  strong  solution  of 
sodium  nitrite  to  a  solution  of  ferrous  chloride  or  sulphate 
in  hydrochloric  acid.  If  the  sodium  nitrite  contains  car- 
bonate, it  may  be  removed  by  precipitation  with  calcium 
chloride.t 

In  order  to  obtain  this  gas  in  a  very  pure  condition,  the 
reaction  which  takes  place  in  a  Lunge's  nitrometer  is  em- 
ployed; namely,  treating  mercury  with  a  mixture  of  sul- 
phuric acid  and  nitric  acid.  The  purity  of  the  gas  was  placed 
beyond  question  by  the  results  obtained  on  leading  it  over 
glowing  copper ;  the  increase  in  weight  of  the  metal,  giv- 
ing the  weight  of  oxygen,  whilst  the  gas  evolved,  which 
was  collected  and  measured,  gave  the  weight  of  nitrogen. 
In  the  reaction  between  copper  and  nitric  oxide,  which 
is  attended  by  the  liberation  of  much  heat,  the  metal  is 
quantitatively  converted  into  cuprous  oxide.J: 


NITROGEN    TETRAOXIDE. 

N304. 

200  grams  arsenious  acid  in  pieces  the  size  of  a  pea 
are  placed  in  a  tubulated  retort  with  bent  neck,  200  grams 
nitric  acid  1.38  sp.  gr.  poured  over  it,  and  very  moderately 


*  By  C.   M.  VAN  DEVENTER,  Ber.  26,  589-593. 
f  By  J.   THIELE,  Annalen  253,  146. 
j  By  F.  ENRICH,  Monatsh,  13,  73-77. 


22  LABORATORY   MANUAL   OF 

warmed.  The  evolved  gas  passes  into  an  empty  wash- 
bottle,  is  then  dried  by  a  tube  filled  with  calcium  nitrate 
and  is  finally  conducted  into  a  wide  combustion-tube  which 
is  surrounded  by  a  freezing  mixture  of  ice  and  common  salt. 
A  dark-green  liquid  condenses  in  this  tube.  Dry  oxygen 
gas  is  conducted  into  it  until  the  liquid  has  changed  to 
a  pure  yellow,  then  the  tube  is  sealed. 

The  arsenic  trioxide  reduces  the  nitric  acid  passing 
into  arsenic  acid.  In  drying  the  gases  calcium  chloride 
must  not  be  used,  as  they  would  be  contaminated  with 
chlorine,  nor  sulphuric  acid,  as  it  absorbs  the  gases. 
The  condensed  mixture  of  nitrogen  trioxide  and  tetroxide 
is  transformed  by  oxygen  into  pure  tetroxide. 

The  liquid  should  show  a  sp.  gr.  of  1.45  and  boil  at 
25  to  26°  C.  On  cooling  rapidly  it  should  stiffen  to  a  color- 
less crystal  mass,  which  melts  at  about  12°  C. 


SULPHURIC     ACID. 
H3SO4  OR  SO2(OH)2. 

a.  Concentrated  pure  sulphuric  acid. 

b.  Concentrated  sulphuric  acid  of  commerce. 

c.  Common  dilute  sulphuric  acid. 

The  following  method  may  be  recommended  for  pre- 
paring chemically  pure  sulphuric  acid  : 

a.  Put  1,000  grams  of  ordinary  concentrated  sulphuric 
acid  in  a  porcelain  dish,  and  3  grams  of  ammonium  sul- 
phate, and  heat  till  copious  fumes  of  SO3  begin  to  escape, 
in  order  to  destroy  the  oxides  of  nitrogen  which  are 
present.  After  cooling,  add  4  or  5  grams  of  powdered 
manganese  dioxide,  and  heat  to  boiling  with  stirring,  in 


INORGANIC    PREPARATIONS.  23 

order  to  convert  any  arsenious  acid  into  arsenic  acid. 
When  cool  pour  off  the  clear  fluid  by  means  of  a  long 
funnel  tube  into  a  retort  coated  with  clay.  The  retort 
should  not  be  more  than  half  full,  and  is  to  be  heated 
directly  over  charcoal.  To  prevent  bumping,  rest  the 
retort  on  an  inverted  crucible  cover,  so  that  the  sides  may 
be  more  heated  than  the  bottom.  The  neck  of  the  retort 
must  reach  so  far  into  the  receiver  that  the  acid,  distilling 
over,  drops  directly  into  the  body.  To  cool  the  receiver 
by  means  of  water  is  unnecessary  and  even  dangerous. 
To  prevent  the  receiver  from  coming  into  actual  contact 
with  the  hot  neck  of  the  retort,  some  asbestos  in  large 
fibres  is  placed  between  them.  When  about  10  or  15 
grams  has  been  drawn  over,  change  the  receiver  and  slowly 
distil  off  three-fourths  of  the  contents  of  the  retort.  This 
method  depends  upon  the  fact  discovered  by  Bussy 
and  Buignet,  that  on  distilling  sulphuric  acid,  which 
contains  arsenic  in  the  form  of  arsenic  acid,  an  arsenic-free 
distillate  is  obtaine'd. 

b.  Pour  into  4  parts  of  water  I  part  of  concentrated 
sulphuric  acid,  and  conduct  into  the  mixture  for  some  time 
a  slow  stream  of  hydrogen  sulphide,  keeping  the  fluid 
heated  to  70°  C.  Let  the  mixture  stand  at  rest  for  several 
days,  then  decant  the  clear  supernatant  fluid  from  the 
precipitate,  which  consists  of  sulphur,  lead  sulphide,  per- 
haps also  arsenic  sulphide,  and  heat  the  decanted  fluid  in  a 
tubulated  retort  with  upturned  neck  and  open  tubulature 
until  sulphuric  acid  fumes  escape  with  the  aqueous 
vapor.  The  acid  so  purified  is  fit  for  many  purposes 
of  chemical  analysis ;  if  it  is  desired,  however,  to  free 
it  also  from  non-volatile  substances,  it  may  be  distilled 


4  LABORATORY    MANUAL   OF 

from  a  coated  retort  as  in  a.  As  soon  as  the  drops  in  the 
neck  of  the  retort  become  oily,  the  receiver  is  changed, 
and  the  concentrated  acid  which  then  passes  over  is  kept 
in  a  separate  vessel. 

c.  Common  dilute  sulphuric  acid. — Add  to  5  parts  of 
water  in  a  thin  glass  or  porcelain  dish  gradually,  and  whilst 
stirring,  I  part  of  concentrated  sulphuric  acid.  The  lead 
sulphate  which  seperates  is  allowed  to  subside,  and  the  clear 
fluid  finally  decanted. 

Pure  sulphuric  acid  must  be  colorless;  when  color- 
less solution  of  ferrous  sulphate  is  poured  upon  it  in  a 
test  tube,  no  brown  tint  must  mark  the  plane  of  contact 
of  the  two  fluids  (nitric  acid,  nitrous  acid) ;  when  diluted 
with  twenty  parts  of  water  it  must  not  impart  a  blue  tint 
to  a  solution  of  potassium  iodide  mixed  with  starch 
paste  (nitrous  acid).  Mixed  with  pure  zinc  and  water, 
it  must  yield  hydrogen  gas,  which,  on  being  passed 
through  a  red-hot  tube,  must  not  deposit  the  slightest 
trace  of  arsenic.  It  must  leave  no  residue  upon  evapora- 
tion on  platinum,  and  must  remain  perfectly  clear  upon 
dilution  with  four  or  five  parts  of  alcohol  (lead,  iron,  calcium). 
The  presence  of  small  quantities  of  lead  is  detected  most 
easily  by  adding  some  hydrochloric  acid  to  the  sulphuric 
acid  in  a  test  tube.  If  the  plane  of  contact  is  marked 
by  turbidity  (lead  chloride),  lead  is  present.  Sulphurous 
acid  is  discovered  by  the  odor  after  shaking  the  acid  in  a 
half-filled  bottle. 


INORGANIC    PREPARATIONS.  25 


HYDROGEN   SULPHIDE.     HYDROSULPHURIC 
ACID.     SULPHURETTED    HYDROGEN. 

H3S. 

Hydrogen  sulphide  is  usually  evolved  from  iron 
sulphide,  which  is  broken  into  small  lumps  and  then 
treated  with  dilute  sulphuric  or  hydrochloric  acid.  Fused 
iron  sulphide  may  be  purchased  cheaply,  or  may  be  made 
by  heating  iron  turnings  or  I  to  I  J^  inch  iron  nails,  in  a 
covered  Hessian  crucible  to  a  white  heat,  and  then  adding 


FIG.  6. 

small  lumps  of  roll-sulphur  until  the  entire  contents  of  the 
crucible  are  in  fusion.  As  soon  as  this  is  the  case,  pour 
the  fused  mass  upon  sand,  or  into  an  old  Hessian  crucible. 
Or  make  a  hole  in  the  bottom  of  the  crucible,  when  the 
iron  sulphide  will  run  through  as  fast  as  it  forms,  and  may 


26  LABORATORY    MANUAL   OF 

be  received  in  a  shovel  placed  in  the  ash-pit.  Or  intro- 
duce an  intimate  mixture  of  thirty  parts  of  iron  filings  and 
twenty-one  parts  of  flowers  of  sulphur  in  small  portions 
into  a  red-hot  crucible,  awaiting  always  the  incandescence 
of  the  portion  last  introduced  before  proceeding  to  the 
addition  of  a  fresh  one.  When  you  have  thus  put  the 
mixture  into  the  crucible,  cover  the  latter  closely,  and 
expose  it  to  a  more  intense  heat,  sufficient  to  make  the 
iron  sulphide  fuse  more  or  less,  then  allow  the  crucible  to 
cool  and  break  the  sulphide  in  small  pieces. 

The  iron  sulphide  is  then  placed  in  a  Kipp's  apparatus, 
fig.  6,  and  the  gas  is  generated  by  the  action  of  dilute 
sulphuric  or  hydrochloric  acids. 

HYDROGEN  SULPHIDE  FREE  FROM  ARSENIC. 

Calcium  sulphide  (prepared  by  igniting  a  mixture  of 
plaster  of  Paris  and  coal)  yields  the  pure  gas  when  treated 
with  dilute  hydrochloric  acid.  To  evolve  the  gas  in  a 
regular  stream,  a  mixture  of  calcium  sulphide,  with  one- 
fourth  of  its  weight  of  plaster  of  Paris  and  enough  water  to 
make  a  cream,  is  poured  into  shallow  paper  trays.  As 
soon  as  it  has  set,  the  cake  is  cut  up  into  blocks,  which 
are  dried  at  a  gentle  heat.  They  may  be  used  in  Kipp's 
apparatus.* 

Another  method  is  to  use  barium  sulphate  (powdered 
barytes)  mixed  with  25  per  cent,  of  ground  coal  and  20 
per  cent,  of  common  salt.  The  dampened  mixture  is 
rammed  into  a  clay  crucible,  which,  after  drying  and 
closing  with  a  luted  cover,  is  heated  for  several  hours 


*  R.  FRESENIUS,  Zeit.  Anal.  Chem.  26,  339. 


(trwivr..  SITYX 

INORGANIC    PREPARATIONS*   >  2 7 

at  an  incipient  white  heat  The  product  is  in  hard  com- 
pact masses  which  dissolve  completely  in  dilute  hydro- 
chloric acid  with  a  steady  evolution  of  hydrogen  sul- 
phide.* 

HYDROGEN    SULPHIDE    FREED    FROM    HYDROGEN 
ARSENIDE. 

This  method  is  based  on  the  fact  that  hydrogen  arsen- 
ide reacts  violently  with  iodine  at  ordinary  temperature, 
arsenious  iodide  and  hydrogen  iodide  being  formed. 

A  narrow  tube,  30  to  40  cm.  long,  is  loosely  filled  with 
coarsely  powdered,  air-dried  iodine  interspersed  with  glass 
wool ;  2  or  3  grams  of  iodine  will  remove  every  trace  of  ar- 
senic from  hydrogen  sulphide  prepared  from  the  ordinary 
impure  materials,  passing  over  it  for  several  days.  In 
purifying  hydrogen,  the  latter  is  subsequently  passed  over 
glass  wool  wetted  with  potassium  iodide  solution  and  then 
through  aqueous  potash. t 

Free  hydrogen  sulphide  in  quantity  is  readily  detected 
by  its  odor,  and  its  blackening  effect  upon  paper  moist- 
ened with  lead  acetate. 


SULPHUR    DIOXIDE. 

S03. 

Prepared  by  gently  heating  in  a  flask  scrap  copper  with 
concentrated,  sulphuric  acid 

Cu  +  2H2SO4  =  SO2  +  2H3O  +  CuSO4. 
It  can  be  absorbed  in  water  and  used  as  a  solution  of  sul- 
phurous   acid    or    absorbed    in    caustic    alkalies    forming 


*  C.   WINKLER,  Zeit.  Anal.  Chem.  27,  26. 
f  O.  JACOBSEN,  Ber.  20,  1999. 


28  LABORATORY    MANUAL   OF 

bisulphites  which  may  be  again  used  to  generate  sulphur 
dioxide  by  the  action  of  cone,  sulphuric  acid. 

Prepared  in  this  way,  however,  it  is  liable  to  contain 
sulphuric  acid  which  is  not  readily  removed.  Sulphur 
dioxide  is  now  obtainable  in  liquified  condition  and  as 
such  is  used  for  disinfecting  and  freezing  purposes. 

Sulphurous  anhydride  (SO2)  can  be  generated  in 
Kipp's  apparatus  by  the  action  of  ordinary  concentrated 
sulphuric  acid  on  cubes  prepared  by  Winkler's  method 
from  a  mixture  of  3  parts  of  calcium  sulphite  and  I  part  of 
plaster.  Economy  in  the  use  of  cubes  is  effected  if  only 
the  number  required  for  the  generation  of  the  amount  of 
gas  needed  are  wetted  with  the  acid  at  the  commencement 
of  the  operation.* 

Sulphur  Dioxide  is  recognized — 

1st.  By  its  odor  which  is  marked  and  well-known,  re- 
sembling that  of  burning  matches. 

2nd.  Suspend  in  the  gas  a  strip  of  paper  which  has 
been  dipped  into  a  solution  of  starch  paste  and  potassium 
iodate.  Iodine  is  liberated  and  the  paper  becomes  blue. 

2KIO3+  5SO3  +  4H2O  ==  2HKSO4  -f  3H3SO4  +  I2. 


CARBON    MONOXIDE. 

CO. 

Prepared  by  gently  heating  commercial  oxalic  acid  in 
a  capacious  flask  with  cone,  sulphuric  acid.  The  acid 
exerts  a  dehydrating  action  and  a  mixture  of  carbon  mon- 
oxide and  carbon  dioxide  is  evolved.  The  mixed  gases  are 


G.  NEUMANN,  Ber.  20,  1584. 


INORGANIC    PREPARATIONS.  29 

passed  through  potassium  hydrate  solution  which  absorbs 
the  carbon  dioxide  and  sulphuric  acid ;  any  water  which 
may  be  present  being  removed  by  passing  the  gases 
through  concentrated  sulphuric  acid. 

Another  and  better  method  is  as  follows : 
A  mixture  of  finely  powdered  potassium  ferrocyanide 
with  eight  or  ten  times  its  weight  of  cone,  sulphuric  acid  is 
heated  in  a  capacious  flask  ;   the  following  reaction  results: 
K4Fe(CN)6  +  6H3SO4  +  6H2O  = 

6CO  +  2K2SO4  4-  3(NH4)2SO4  +  FeSO4. 

If  the  heat  is  carefully  regulated  the  evolution  of  gas  is 
gentle  and  regular.  The  product,  however,  is  liable  to 
contain  carbon  dioxide  and  cyanogen  compounds,  hence  it 
is  better  to  wash  with  potassium  hydrate.  Carbon  mon- 
oxide is  recognized  when  in  sufficient  quantities  by  the 
bluish  flame  with  which  it  burns. 


CARBON    DIOXIDE. 
CO2. 

Prepared  by  treating  coarsely  broken  marble  with  di- 
lute acids  in  Kipp's  Apparatus,  washed  with  water  and  dried 
over  cone,  sulphuric  acid.  It  is  used  to  remove  chlorine  in 
various  operations  where  heat  is  undesireable.  The  gas 
may  now  be  obtained  in  the  liquid  form,  in  steel  cylin- 
ders and  is  used  as  a  freezing  agent. 

The  free  gas  is  detected  by  conducting  it  through  a 
solution  of  calcium  hydroxide,  Ca(OH)2  with  which  it 
forms  a  white  precipitate  (calcium  carbonate). 

The  free  gas  in  water  may  be  detected  by  adding  the 
same  solution  as  above. 


30  LABORATORY    MANUAL    OF 


SIMPLE  AND  RAPID  PREPARATION  OF  PURE  GASES. 

Instead  of  using  an  acid  for  the  evolution  of  carbonic 
anhydride,  sulphurous  anhj'dride,  and  similar  gases,  it  is 
convenient  to  use  sodium  hydrogen  sulphate.  A  mixture 
of  equivalent  quantities  of  the  respective  salts  in  powder 
gives,  when  wetted  with  water,  a  regular  stream  of  the  re- 
quired gas,  which  will  be  free  from  the  impurities  usually 
derived  from  the  use  of  an  acid.* 


AMMONIA, 
NH3. 

AMMONIUM    HYDRATE. 
NH4OH. 

Prepared  by  gently  heating  crude  ammonium  sulphate 
with  dry  slaked  lime 

2NH4C1  -f  Ca(OH)2  =  2NH3  +  CaClg  4-  2H2O 

2NH3  +  2H2O  =  2NH4OH. 

If  gaseous  ammonia  is  needed  it  must  be  caught  by 
downward  displacement  of  air,  otherwise  the  gas  is  passed 
into  water  until  saturated. 

To  make  ammonia  for  laboratory  use  the  strongest 
ammonia  water  is  dropped  on  porous  calcium  chloride, 
great  heat  is  evolved  during  this  operation  but  the  gas 
which  passes  over  is  almost  pure. 


*  By  H.  BORNTRAEGER,  Zeit.  Anal.  Chem.,  29,  140. 


INORGANIC    PREPARATIONS.  31 


POTASSIUM     HYDROXIDE,    OR    POTASSA, 

KOH, 

AND    SODIUM    HYDROXIDE,   OR    SODA, 
NaOH. 

The  preparation  of  perfectly  pure  potassa  or  soda  is  a 
difficult  operation.  It  is  advisable,  therefore,  to  provide 
besides  perfectly  pure  caustic  alkali,  some  which  is  not 
quite  pure,  and  some  which,  being  free  from  certain  im- 
purities, may  in  many  cases  be  substituted  for  the  pure  sub- 
stance. 

a.  Common  solution  of  Soda. — Put  into  a  clean  cast-iron 
pan  provided  with  a  lid,  3  parts  of  crystallized  sodium  car- 
bonate of  commerce  and  I  5  parts  of  water,  heat  to  boiling, 
and  add,  in  small  portions  at  a  time,  thick  milk  of  lime  pre- 
pared by  pouring  3  parts  of  warm  water  over  I  part  of 
fresh-burned  quick-lime,  and  letting  the  mixture  stand  in 
a  covered  vessel  until  the  lime  is  reduced  to  a  uniform 
pulpy  mass.  Keep  the  liquid  in  the  pan  boiling  while 
adding  the  milk  of  lime,  for  a  quarter  of  an  hour 
longer ;  then  filter  off  a  small  portion,  and  try  whether  the 
filtrate  still  causes  effervescence  in  hydrochloric  acid.  If 
this  is  the  case,  the  boiling  must  be  continued,  and  if 
necessary  some  more  milk  of  lime  must  be  added  to  the 
fluid.  When  the  solution  is  perfectly  free  from  carbonic 
acid,  cover  the  pan,  allow  the  fluid  to  cool  a  little,  and 
then  draw  off  the  nearly  clear  solution  from  the  residuary 
sediment,  by  means  of  a  siphon  filled  with  water,  and 


32  LABORATORY    MANUAL   OF 

transfer  it  to  a  glass  flask.  Boil  the  residue  a  second  and 
third  time  with  water,  and  draw  off  the  fluid  in  the  same 
way.  Cover  the  flask  close  with  a  glass  plate,  and  allow 
the  lime  suspended  in  the  fluid  to  subside  completely. 
Scour  the  iron  pan  clear,  pour  the  clear  solution  back  into 
it,  and  evaporate  it  to  6  or  7  parts.  The  solution  so  pre- 
pared contains  from  9  to  10  per  cent,  of  soda,  and  has 
a  specific  gravity  of  from  1.13  to  1.15.  If  it  is  wished  to 
filter  a  solution  of  soda  which  is  not  quite  clear,  a  cov- 
ered funnel  should  be  used,  which  has  been  charged  first 
with  lumps  of  white  marble  and  then  with  powder  of  the 
same,  the  fine  dust  being  rinsed  out  with  water  before  the 
filter  is  used  (Graeger).  Solution  of  soda  must  be  clear, 
colorless,  and  as  free  as  possible  from  carbonic  acid  ;  am- 
monium sulphide  must  not  impart  a  black  color  to  it. 
Traces  of  silicic  acid,  alumina,  and  phosphoric  acid  are  usu- 
ally found  in  a  solution  of  soda  prepared  in  this  manner, 
on  which  account  it  is  unfit  for  use  in  accurate  experi- 
ments. Solution  of  soda  is  kept  best  in  bottles  closed  with 
ground  glass  caps.  In  default  of  capped  bottles,  common 
ones  with  well-ground  stoppers  may  be  used,  in  which  case 
the  neck  must  be  wiped  perfectly  dry  and  clean  inside  and 
the  stopper  coated  with  paraffine ;  since,  if  this  precaution 
is  neglected,  it  will  be  found  impossible  after  a  time  to 
remove  the  stopper,  particularly  if  the  bottle  is  only  rarely 
opened. 

Absolutely  pure  soda  is  best  prepared  by  dissolving 
sodium  in  pure  water  in  a  silver  dish  and  evaporating  un- 
til a  drop  of  the  liquid  solidifies  on  cooling. 

The  strength  of  the  caustic  soda  solution  is  ascertained 
approximately  by  specific  gravity. 


INORGANIC   PREPARATIONS.  33 

%  NaOH.  Sp.  Gr.  %  NaOH.  Sp.  Gr. 

IO 1.11$  21 1-236 

II I.I26  22 1-247 

12 1.137  23 T-258 

13 1.148  24 1.269 

i4--  --1-159  25 J-279 

15 1.170  26 1.290 

16 1.181  27 1-300 

17 1.192  28 1.310 

1 8 i. 202  29 1-321 

'9  •-  ...1.213  30 1.332 

20 1.225 

The  exact  strength  may  be  determined  by  titrating 
say  20  c.  c.  of  the  solution  with  normal  acid,  using  phen- 
olphthalein  as  indicator,  if  any  carbonic  acid  is  present,  a 
small  quantity  of  barium  chloride  solution  should  be 
added  before  titrating.  The  calculation  is  very  simple 
since  i  c.  c.  N/HC1  or  N/2H2SO4  =  0.040  gram.  NaOH  or 
0.0561  KOH. 

b,  Potassa  purified  with  alcohol. — Dissolve  some  caus- 
tic potassa  of  commerce  in  alcohol,  in  a  stoppered  bottle, 
by  digestion  and  shaking ;  let  the  fluid  stand,  decant  it,  or 
filter  it  if  necessary,  and  evaporate  the  clear  fluid  in  a  sil- 
ver dish  over  the  gas  or  spirit  lamp  until  no  more  vapors 
escape,  adding  from  time  to  time,  during  the  evaporation, 
some  water  to  prevent  blackening  of  the  mass.  Place  the 
silver  dish  in  cold  water  until  it  has  sufficiently  cooled  ;  re- 
move the  cake  of  potassa  from  the  dish,  break  in  coarse 
lumps  in  a  hot  mortar  and  keep  in  a  well  closed  glass  bot- 
tle. When  required  for  use,  dissolve  a  small  lump  in 
water. 


34  LABORATORY    MANUAL   OF 

The  potassa  so  prepared  is  sufficiently  pure  for  most 
purposes ;  it  contains  a  minute  trace  of  alumina,  but  is 
usually  free  from  phosphoric,  sulphuric,  and  silicic  acids. 
The  solution  must  remain  clear  upon  addition  of  ammonium 
sulphide  ;  hydrochloric  acid  must  only  produce  a  barely 
perceptible  effervescence  in  it.  The  solution  .acidified  with 
hydrochloric  acid  must,  upon  evaporation  to  dryness,  leave 
a  residue  which  dissolves  in  water  to  a  clear  fluid.  The 
solution  acidified  with  hydrochloric  acid,  and  then  mixed 
with  ammonia  in  the  least  possible  excess,  must  not  show 
any  flocks  of  alumina,  at  least  until  it  has  stood  in  a  warm, 
place  for  several  hours.  The  solution  acidified  with  nitric 
acid  must  not  give  any  precipitate  with  a  nitric  acid  solu- 
tion of  ammonium  molybdate. 

Potassa  prepared  with  baryta. — Dissolve  pure  crystals 
of  baryta  by  heating  with  water,  and  add  to  the  solution 
pure  potassium  sulphate  until  a  portion  of  the  filtered  fluid, 
acidified  with  hydrochloric  acid  and  diluted,  no  longer 
gives  a  precipitate  on  addition  of  a  further  quantity  of  the 
sulphate  (16  parts  of  crystals  of  baryta  require  9  parts  of 
potassium  sulphate).  Let  the  turbid  fluid  clear,  decant 
and  evaporate  in  a  silver  dish.  The  potassa  so  prepared 
is  perfectly  pure,  except  that  it  contains  a  trifling  admix- 
ture of  potassium  sulphate,  which  is  left  behind  upon  dis- 
solving in  a  little  water.  It  is  but  rarely  required,  its  use 
being  in  fact  exclusively  confined  to  the  detection  of 
minute  traces  of  alumina, 


INORGANIC   PREPARATIONS.  35 


BARIUM     HYDROXIDE,    OR     BARYTA. 

Ba(OH)2. 

There  are  many  ways  of  preparing  baryta;  but 
as  witherite  (barium  carbonate)  is  now  cheaply  procurable, 
the  following  method  is  preferable:  Mix  intimately  to- 
gether 100  parts  of  finely  pulverized  witherite,  10  parts 
of  charcoal  in  powder,  and  5  parts  of  rosin,  put  the  mix- 
ture in  an  earthenware  crucible,  lute  on  the  lid  with  clay, 
and  expose  the  crucible  so  prepared  to  the  heat  of  a  brick- 
kiln. Break  and  triturate  the  baked  mass,  boil  repeatedly 
with  water  in  an  iron  pot,  filter  into  bottles,  stopper,  and 
let  them  stand  in  the  cold,  when  large  quantities  of  crystals 
of  barium  hydroxide  Ba(OH)2  -f  8H3O  will  make  their 
appearance.  Let  the  crystals  drain  in  covered  funnels, 
dry  rapidly  between  sheets  of  blotting  paper,  and  keep 
them  in  well  closed  bottles.  For  use,  dissolve  I  part  of  the 
crystals  in  20  parts  of  water,  with  the  aid  of  heat,  and  filter 
the  solution.  The  baryta  water  so  prepared  is  purer  than 
the  mother  liquor  running  off  from  the  crystals.  The  res- 
idue, which  is  insoluble  in  water  and  consists  of  undecom- 
posed  witherite  and  charcoal,  may  be  turned  to  account  in 
the  preparation  of  barium  chloride. 

Baryta  water  must,  after  precipitation  of  the  barium 
by  pure  sulphuric  acid,  give  a  filtrate  remaining  clear  when 
mixed  with  alcohol,  and  leaving  no  fixed  residue  upon 
evaporation  in  a  platinum  crucible. 

Barium  hydroxide  being  a  strong  base,  precipi- 
tates the  metallic  hydroxides  insoluble  in  water  from  the 
solutions  of  their  salts. 

S       "  OF  THE  A 

UNIVERSITY) 


36  LABORATORY    MANUAL   OF 


CALCIUM    HYDROXIDE,    OR    LIME. 
Ca(OH)2. 

Calcium  hydroxide  is  obtained  by  slacking  lumps  of 
pure  calcined  lime  in  a  porcelain  dish,  with  half  their 
weight  of  water.  The  heat  which  accompanies  the  com- 
bination of  the  lime  and  the  water  is  sufficient  to  evapor- 
ate the  excess  of  water.  Slacked  lime  must  be  kept  in  a 
well-stoppered  bottle. 

To  prepare  lime  water,  digest  slacked  lime  for  some 
time  with  cold  distilled  water,  shaking  the  mixture  occa- 
sionally ;  let  the  undissolved  portion  of  lime  subside,  de- 
cant, and  keep  the  clear  fluid  in  a  well-stoppered  bottle. 
If  it  is  wished  to  have  the  lime  water  quite  free  from  all 
traces  of  alkalies,  baryta  and  strontia,  which  are  almost 
invariably  present  in  slacked  lime  prepared  from  calcined 
limestone,  the  liquids  of  the  first  two  or  three  decantations 
must  be  removed,  and  the  fluid  decanted  afterwards  alone 
made  use  of. 

Lime  water  must  imp'art  a  strongly-marked  brown 
tint  to  turmeric  paper,  and  give  a  not  too  inconsider- 
able precipitate  with  sodium  carbonate.  It  speedily  loses 
these  properties  upon  exposure  to  the  air. 


LEAD     DIOXIDE. 

Pb02. 

a.  In  the  dry  way.  53  grams  lead  oxide  are  thor- 
oughly mixed  in  a  mortar  with  50  grams  calcium  carbonate, 
and  a  wide  and  not  too  deep  clay  crucible  is  filled  loosely 


INORGANIC    PREPARATIONS. 


37 


with  the  mixture  and  heated  in  Roessler's  gas  furnace  (fig. 
7)  for  half  an  hour  to  fusion,  regulating  the  draft  so  that 
there  shall  be  an  excess  of  air  in  the  fusion  chamber. 
After  having  cooled  the  slightly  baked  frit,  it  is  powdered 


FIG.  7. 

in  a  mortar  and  once  more  heated  for  half  an  hour  at  a  red 
heat.  A  powdered  sample  of  the  product  is  covered  with 
diluted  HNOs;  if  carbonic  acid  is  evolved,  the  powdered 
mass  is  to  be  heated  a  short  while  longer  to  white  heat* 


*  The  oxydation  goes  on  rapidly,  if  the  mixture  is  heated  in  an  infusi- 
ble clay  dish  (iron  is  impracticable,  as  it  corrodes  rapidly  in  Roessler's  gas 
furnace  at  a  high  temperature).  As  soon  as  the  mass  begins  to  glow,  stir 
vigorously  with  an  iron  spatula.  During  the  process  the  small  opening  in 
the  cover  of  the  furnace  is  not  closed. 


38  LABORATORY    MANUAL   OF 

The  finely  powdered,  flesh-colored  calcium  plumbate  is 
poured  gradually  into  200  c.  c.  diluted  HNO3;  after  set- 
tling, it  is  decanted  and  ground  in  a  mortar  with  fresh 
HNO3  (100  c.  c.).  Finally  it  is  once  more  boiled  up  with 
diluted  HNO.3,  filtered,  rinsed  with  hot  water  and  dried  on 
the  waterbath.  For  most  purposes  it  is  more  convenient 
to  merely  decant  the  peroxide  with  hot  water  and  preserve 
it  as  paste.  The  weight  of  the  lead  peroxide  obtained 
about  equals  that  of  the  lead  oxide  taken.* 

b.  In  the  ivet  way.  A  solution  of  190  grams  lead 
acetate  in  500  c.  c.  water  is  placed  into  500  c.  c.  of  20% 
soda  lye  and  the  cooled  milky,  alkaline  solution  treated  by 
shaking  with  chlorine  until  no  further  precipitation  takes 
place.  It  is  then  decanted  with  water  and  purified,  as 
above,  with  nitric  acid. 

By  the  aid  of  atmospheric  oxygen  and  lead  oxide, 
the  carbonic  acid  of  the  calcium  carbonate  is  expelled  with 
formation  of  calcium  plumbate  corresponding  with  the  ortho- 
silicates  :  2CaCO3  +  PbO  +  O  =  Ca2PbO4  +  2CO2.  The 
plumbate  varying  only  very  little  in  color  from  the  original 
mixture,  is  easily  decomposed  with  HNO3:  Ca2PbO4  -f 
4HNO3  =  2Ca(NO3)2  +  PbO2  4-  2H3O. 

In  watery  solution  lead  peroxide  is  formed  through 
the  action  of  chlorine  on  sodium  lead  oxide:  Pb(ONa)2  + 
2C1  ==  PbO2  +  2NaCl. 

The  dark-brown  lead  peroxide,  after  being  boiled  with 
diluted  HNO3,  must  not  impart  a  violet  color  to  the  super- 
natant solution;  this  color  should  appear  immediately 
upon  adding  a  drop  of  diluted  manganese  sulphate  solu- 


*  KASSNER,  Chem.  Ind.  13,  1890,  104-120. 


INORGANIC    PREPARATIONS.  39 

tion.*  Suspended  in  diluted  HNO3,  it  should  dissolve 
readily  and  entirely  upon  addition  of  sodium  nitrite.  To 
determine  the  quantity  of  lead  peroxide,  an  average  sam- 
ple of  the  paste  or  the  finely  powdered  preparation  is 
weighed,  placed  into  a  flask  with  ground  glass  stopper, 
covered  with  diluted  HNO3  and  gradually  add  a  small  ex- 
cess of  normal  sodium  nitrite,  aiding  the  reaction  by  fre- 
quent and  vigorous  shaking  of  the  closed  bottle.  After  all 
the  peroxide  has  passed  into  solution,  it  is  diluted  with  a 
large  quantity  of  water  and  the  excess  of  nitrite  titrated 
back  with  potassium  permanganate. 

Lead  dioxide,  when  boiled  with  thrice  its  bulk 
of  pure  nitric  acid  for  several  minutes  and  allowed  to 
settle,  must  not  communicate  the  faintest  red  color  to  the 
acid  (absence  of  manganese). 


LEAD    CARBONATE. 

PbCO;{. 

Lead  oxide  is  readily  converted  into  soluble  hydroxide 
on  treatment  with  a  moderately  concentrated  solution  of 
magnesium  acetate.  The  solution  thus  obtained  has  an 
alkaline  reaction,  and  yields  lead  carbonate  when  treated 
with  carbonic  anhydride.  The  white  precipitate  is  col- 
lected, washed  and  dried,  and  the  solution  of  magnesium 
acetate  concentrated  and  used  for  another  operation.! 


*  Manganese  protoxide  is  oxydized  in  nitric  solution  by  lead  peroxide 
into  permanganic  acid,  PbO2+  HNO2  -f  HNOa=  Pb(NO3)3  -f  II2O. 
f  W.   KUBEL,   Dingl.   Polyt.  J.  262.  143. 


40  LABORATORY    MANUAL   OF 


LEAD    TETRACHLORIDE. 
Pb.Cl4. 

When  lead  dichloride  is  suspended  in  hydrochloric  acid 
and  gaseous  chlorine  passed  into  the  liquid,  a  solution  of 
lead  tetrachloride  is  obtained,  from  which,  on  addition  of 
ammonium  chloride,  a  compound,  PbCl3NH4Cl,  analogous 
to  ammonium  stanic  chloride,  separates.  If  this  com- 
pound is  added  to  concentrated  sulphuric  acid,  an  en- 
ergetic reaction  ensues,  and  lead  tetrachloride  separates  as 
an  oily  substance ;  it  is  purified  by  shaking  with  fresh 
quantities  of  sulphuric  acid.  In  the  pure  state,  it  is  a 
translucent,  yellow,  highly  refractive  liquid  which  fumes 
in  contact  with  moist  air,  with  decomposition  into  lead 
dichloride  and  chlorine ;  it  may  be  kept  under  cold  con- 
centrated sulphuric  acid,  but  when  heated  with  it,  it  de- 
composes with  explosion  into  lead  dichloride  and  chlorine. 
When,  however,  lead  tetrachloride  is  heated  in  a  retort 
with  concentrated  sulphuric  acid,  and  a  current  of  chlorine 
passes  through,  a  certain  quantity  of  the  tetrachloride  distils 
over  below  105°  C.,  at  about  which  temperature  explosion 
occurs.  The  sp.  gr.  of  lead  tetrachloride  at  o°  C.  is  3.18, 
and  it  solidifies  to  a  yellowish  crystalline  mass  at  15°  C.;  it 
forms  a  hydrate  in  the  presence  of  a  little  water,  which,  by 
the  further  addition  of  water,  decomposes  into  lead  perox- 
ide and  hydrogen  chloride ;  when  brought  in  contact  with 
a  small  quantity  of  cooled  hydrochloric  acid,  a  crystalline 
derivative,  probably  PbCl42HCl,  is  formed. 


*  By  H.  FRIEDRICH,  Ber.  26,  1434-1436;  compare  Abetr.,  1890,  699; 
also  CLASSEN  AND  ZAHORSKI,  Zeit.  anorg.  Chera.  4,  100. 


INORGANIC    PREPARATIONS.  41 


BISMUTH    HYDROXIDE. 

BiOOH. 

Dissolve  bismuth,  freed  from  arsenic  by  fusion  with 
hepar  sulphuris,  in  dilute  nitric  acid ;  dilute  the  solu- 
tion until  a  slight  permanent  precipitate  is  produced ; 
filter  and  evaporate  the  filtrate  to  crystallization.  Wash 
the  crystals  with  water  containing  nitric  acid,  triturate 
them  with  water,  add  ammonia  in  excess,  and  let  the  mix- 
ture digest  for  some  time ;  then  filter,  wash  and  dry  the 
white  precipitate. 

The  bismuth  hydroxide  is  dissolved  in  dilute  nitric 
acid  and  precipitated  with  sulphuretted  hydrogen.  Part 
of  the  precipitated  sulphide  is  treated  with  ammonia  and 
filtered,  and  part  treated  with  ammonium  sulphide  and 
filtered.  The  filtrates  are  then  mixed  with  hydrochloric 
acid  in  excess ;  the  first  should  give  no  precipitate  and  the 
second  only  a  white  precipitate  of  sulphur. 


AMMONIUM    SULPHIDE. 

a.    Colorless  ammonium  monosulphide.      (NH4)2S. 

a.  Transmit  hydrogen  sulphide  through  3  parts  of 
ammonia  solution  until  no  further  absorption  takes 
place ;  then  add  2  parts  more  of  the  same  ammonia 
solution.  The  action  of  hydrogen  sulphide  upon  ammonia 
gives  rise  to  the  formation,  first,  of  (NH4)2S,  (2NH4OH) 
and  H2S  =  (NH4)2S  and  2(H2O)],  then  of  NH4SH ;  upon 
addition  of  the  same  quantitv  of  solution  of  ammonia  as 


42  LABORATORY    MANUAL    OF 

has  been  saturated,  the  ammonia  decomposes  with  the  am- 
monium hydrosulphide  and  ammonium  monosulphide  is 
formed,  thus:  NH4SH  +  NH4OH  =  (NH4)3S  +  H3O. 
The  rule,  however,  is  to  add  only  two-thirds  of  the  quan- 
tity of  solution  of  ammonia,  as  it  is  better  the  prepara- 
tion should  contain  a  little  ammonium  hydrosulphide  than 
that  free  ammonia  should  be  present.  To  employ  am- 
monium hydrosulphide  instead  of  the  simple  monosulphide 
is  unnecessary,  and  tends  to  increase  the  smell  of  sulphur- 
etted hydrogen  in  the  laboratory,  as  the  preparation  al- 
lows that  gas  to  escape  when  in  contact  with  metallic  acid 
sulphides. 

Ammonium  sulphide  should  be  kept  in  well- corked 
vials.  It  is  colorless  at  first,  and  deposits  no  sulphur  upon 
addition  of  acids.  Upon  exposure  to  the  air,  however,  it 
acquires  a  yellow  tint,  owing  to  the  formation  of  am- 
monium disulphide,  which  is  attended  also  with  formation 
of  ammonia  and  water,  thus:  2(NH4)3S  +  O  =  (NH4)3S3 
+  2NH3  +  H3O.  Continued  action  of  the  oxygen  of  the 
air  upon  the  ammonium  sulphide  tends  at  first  to  the  for- 
mation of  still  higher  sulphides  ;  but  afterwards  the  fluid 
deposits  sulphur,  and  finally  all  the  ammonium  sulphide  is 
decomposed  and  the  solution  contains  nothing  but  am- 
monia and  ammonium  thiosulphate.  The  formation  of 
thiosulphate  proceeds  thus:  (NH4)3S3  4-  O3  =  (NH4)3S2O3. 

b.    Yelloiv  ammonium  poly  sulphide.     (NH4)3SX. 

b.  The  ammonium  sulphide  which  has  turned  yellow 
by  moderate  exposure  to  the  air  may  be  used  for  all  pur- 
poses requiring  the  employment  of  yellow  ammonium 
sulphide.  The  yellow  sulphide  may  also  be  expeditiously 
prepared  by  digesting  the  monosulphide  with  some  sul- 


INORGANIC   PREPARATIONS.  4$ 

phur.  All  kinds  of  yellow  ammonium  sulphide  deposits 
sulphur  and  look  turbid  and  milky  on  being  mixed  with 
acids. 

Ammonium  sulphide  must  strongly  emit  the  odor 
peculiar  to  it;  with  acids  it  must  evolve  abundance  of 
sulphuretted  hydrogen  ;  the  evolution  of  gas  may  be 
attended  by  the  separation  of  a  pure  white  precipitate,  but 
no  other  precipitate  must  be  formed.  Upon  evaporation 
and  exposure  to  a  red  heat  in  a  platinum  dish  it  must 
leave  no  residue.  It  must  not,  even  on  heating,  precipi- 
tate or  render  turbid  solution  of  magnesium  sulphate  or 
solution  of  calcium  chloride  (free  ammonia,  ammonium 
carbonate). 


SODIUM    SULPHIDE. 

Na2S. 

POTASSIUM    SULPHIDE. 

K3S. 

Preparation  same  as  for  ammonium  sulphide,  except 
that  solutions  of  soda  or  potassa  are  substituted  for  the 
ammonia.  Filter,  if  necessary,  and  keep  the  fluid  obtained 
in  well-stoppered  bottles.  If  required  to  contain  some 
higher  sulphides,  digest  with  powdered  sulphur. 


AMMONIUM    OXALATE. 

(NH4)3C204,  2Aq. 

Dissolve   commercial   oxalic  acid   to  saturation  in  hot 
hydrochloric   acid    of    10   to    12   per   cent.,    cool    rapidly 


44  LABORATORY   MANUAL   OF 

with  constant  agitation,  wash  the  crystals  (best  with 
help  of  a  filter  pump)  with  cold  water  to  remove 
most  of  the  hydrochloric  acid,  redissolve  in  hot  water,  fil- 
ter hot  to  separate  dirt,  cool  again  with  stirring,  and  wash 
the  crystals  with  cold  water  until  chlorine  is  mostly  re- 
moved.* 

Dissolve  the  pure  oxalic  acid  in  2  parts  of  distilled 
water,  with  the  aid  of  heat,  add  solution  of  ammonia  until 
the  reaction  is  distinctly  alkaline,  and  put  the  vessel  in  a 
cold  place.  Let  the  crystals  drain.  The  mother  liquor 
will,  upon  proper  evaporation,  give  another  crop  of  crys- 
tals. 

The  solution  of  ammonium  oxalate  must  not  be 
precipitated  nor  rendered  turbid  by  hydrogen  sulphide,  nor 
by  ammonium  sulphide.  Ignited  on  platinum,  the  salt 
must  volatilize  without  leaving  a  residue. 


SODIUM    ACETATE. 
NaC2H3O2  3Aq. 

Dissolve  crystallized  sodium  carbonate  in  a  little  water, 
add  to  the  solution  acetic  acid  to  slight  excess,  evaporate 
to  crystallization,  and  purify  the  salt  by  recrystallization. 

Sodium  acetate  must  be  colorless  and  free  from  empy- 
reumatic  matter  and  inorganic  acids. 


*  STOLBA. 


INORGANIC    PREPARATIONS.  45 


PURE    SODIUM    CHLORIDE. 
NaCl. 

500  grams  common  salt  and  1500  c.  c.  cold  water  are 
ground  together  in  a  mortar  holding  3  litres,  filtered 
through  a  folded  filter  into  a  porcelain  dish  of  about  3  litres 
capacity  and  heated  on  a  gas  stove.  Now  add  milk  of  lime 
prepared  from  5  grams  caustic  lime  and  mix  with  barium 
chloride  solution  in  small  excess.  After  settling,  it  is 
filtered  into  a  beaker  and  the  clear  fluid  precipitated  with 
soda  solution  (prepared  from  1 5  grams  pure,  dry  sodium  car- 
bonate). The  filtrate  is  neutralized  at  a  boiling  heat  with 
dilute  hydrochloric  acid  (about  25  c.  c.)  and  as  quickly  as 
possible  evaporated  over  a  large  burner  to  j£  litre.  The 
separated  sodium  chloride  is  collected  on  a  funnel  fitted  with 
a  platinum  cone,  sucked  dry  with  the  filter  pump  and  the 
salt  further  dried  by  warming  in  a  platinum  or  porcelain 
dish,  stirring  constantly  with  a  platinum  spatula  or  glass  rod. 

The  magnesium  and   iron   contained    in  the   common 
salt  are  precipitated  by  the  calcium  hydrate  as  hydroxides. 
MgClg  -t-  Ca(OH)3  =  Mg(OH)3  +  CaClg. 

The  sulphuric  acid  precipitated  by  the  barium  chloride. 
CaSO4  4-  BaCl3  =  BaSO4  4  CaCl3. 

The  alkaline  earths  finally  separated  as  carbonates. 
CaCl3  +  Na3CO3  =  CaCO3  4  2NaCl. 

Sodium  chloride  forms  a  snow-white  crystalline  powder 
consisting  of  small  squares.  The  dried  salt  warmed 
in  small  dry  tubes  should  not  decrepitate ;  and  at  a 


46  LABORATORY    MANUAL   OF 

higher  temperature  it  should  melt  to  a  perfect  liquid.  The 
watery  solution  should  be  examined  with  ammonium  oxa- 
late,  sodium  phosphate,  potassium  ferrocyanide  and  barium 
chloride  for  presence  of  calcium,  magnesia,  iron  and  sul- 
phuric acid.  One  drop  of  the  solution  with  ten  drops 
platinum  chloride  evaporated  to  a  small  volume  on  a 
watch-glass  yields  upon  cooling  nice  triclinic  prisms  of  so- 
dium platinic  chloride,  NagPtClg-l- 6Aq,  which,  on  solution 
in  alcohol,  must  not  leave  any  residue  of  potassium  platinic 
chloride.* 


SODIUM. 

Sodium,  which  when  kept  under  mineral  oil  has  be- 
come covered  with  a  crust,  is  easily  purified  by  immersing 
in  a  mixture  of  amyl  alcohol  (i  part)  and  petroleum  (3 
parts)  and  rubbing  with  a  rag  soaked  in  the  same  mixture 
until  it  acquires  a  silvery  lustre.  It  is  then  laid  in  petro- 
leum containing  5  per  cent,  of  amyl  alcohol,  washed  with 
pure  petroleum  and  kept  in  petroleum  containing  0.5  to  I 
per  cent,  of  amyl  alcohol.  The  bright  metal  becomes 
slowly  covered  with  a  film  of  sodium  of  amyloxide,  which 
is,  however,  easily  rubbed  off  with  filter  paper.  Potassium 
and  lithium  can  be  purified  in  the  same  way  and  thus 
keep  their  metallic  lustre  for  a  long  time. 


*  On  an  average  12  g.  crystallized  barium  chloride  are  used.  As  the 
conclusion  of  the  reaction  is  only  recognized  with  difficulty,  in  the  muddy 
solution,  you  can  take  here,  as  in  many  other  cases,  conveniently  small 
samples  from  the  top  of  the  liquid  by  dipping  in  a  fine  capillary  tube.  The 
capillary  is  blown  out  on  to  a  watch-glass.  In  the  present  case  the  watch- 
glass  is  placed  on  a  black  support  and  tested  with  a  drop  of  BaCl2  solution, 
which  will  form  BaSO4  if  H2SO4  be  present. 


OF  THE 

{  UNIVER 
INORGANIC    PREPARATIONS.  47 

Sodium  cleaned,  as  above,  combines  at  once  with  mer- 
cury with  evolution  of  light.  The  liquid  alloy  of  sodium 
and  potassium  is  easily  prepared  by  pressing  together  the 
two  clean  metals  under  a  mixture  of  amyl  alcohol  (i  part), 
and  petroleum  (9  parts).  Sodium  sulphide  is  also  easily 
prepared  by  rubbing  the  clean  metal  (i  gram)  and  salt  3 
grams)  to  a  fine  powder,  and  then  mixing  with  sulphur 
(0.7  gram),  care  being  taken  to  avoid  any  pressure.  When 
the  two  substances  are  intimately  mixed,  combination  sud- 
denly takes  place  with  evolution  of  light.  If  the  mixture 
of  sodium  powder  and  salt  be  mixed  with  sulphur  in  the 
proportions  required  to  form  the  di-  or  tri-sulphide,  the  re- 
action takes  place  more  quickly  and  violently. 

Selenium  and  tellurium  behave  in  the  same  way  as  sul- 
phur when  mixed  with  sodium  powder.* 


SODIUM    AMALGAM. 

(10%). 

Heat  3  kilos  of  mercury  in  a  covered  iron  pot  and 
gradually  add  300  grams  of  sodium,  in  pieces  of  about 
5  grams  each.  On  the  addition  of  each  piece  of 
sodium  there  is  a  violent  action;  toward  the  close  of  the 
operation  it  is  usually  necessary  to  increase  the  heat  and 
stir  the  mass  to  produce  this  reaction.  It  is  not  advisable 
to  clean  the  sodium,  as  the  oxide  is  reduced  during  the 
operation  and  loss  avoided.  (During  the  operation  glasses 
should  be  worn  to  protect  the  eyes.) 


By  M.   ROSENFELD,   Ber.  24,  1658. 


48  LABORATORY    MANUAL    OF 

When  no  further  reaction  takes  place  after  stirring,  the 
melted  mass  is  poured  out  on  a  clean  iron  plate,  broken  as 
soon  as  solid  and  while  still  warm,  packed  in  small  tightly 
closing  glass-stoppered  bottles. 

Sodium  Amalgam  is  used  as  a  means  of  generating 
small  quantities  of  hydrogen  for  reducing  purposes.  (See 
Hydrogen,  page  9). 


SOD'IUM    CARBONATE. 

(Na2CO310Aq.) 

It    is   best    to  provide   this   salt   in   several   grades    of 
purity,  as  follows : 

a.  Free  from  sulphur  and  chlorine.     Finely  pulverize 
"  bicarbonate  of  soda  "  of  commerce,  put  the  powder  into 
a  funnel  stopped  loosely  with  some  cotton,  make  the  sur- 
face even,  cover  it  with   a  disk   of  thick   filter  paper  with 
turned-up  edges,  and  wash  by  pouring  small  quantities  of 
water  on   the  paper   disk  until  the  filtrate,  when  acidified 
with  nitric  acid,  is  not  rendered  turbid  by  solution  of  silver 
nitrate,  nor  by  solution   of  barium  chloride.      Let  the  salt 
dry,  and  then  convert  it  by  gentle  ignition  into  the  simple 
carbonate.     This   is   effected   best  in   a  vessel  of  silver  or 
platinum ;  but   it  may  be   done   also   in  a  perfectly  clean 
iron,  or,  on  a  small  scale,  in  a  porcelain  dish. 

b.  Free  from  silica.     The  salt,  as  prepared  in  a,  is  liable 
to   contain   silica   as  well  as   sand   and   dirt.      To  purify  it 
further,  dissolve  in   twice   its  weight  of  water,  or  dissolve 
"sal  soda"  crystals  in  their  own  weight  of  water,  filter,  and 
pass  into  the  cold  solution  washed    pure  carbon  dioxide, 
but  not  to  complete  saturation. 


INORGANIC    PREPARATIONS.  49 

The  crystals  of  hydrogen  sodium  carbonate  that  sep- 
arate are  drained  in  a  funnel,  washed  with  cold  water, 
dried,  and  gently  ignited,  as  above  directed,  as  long  as 
water  is  given  off.  Prepared  in  glass  vessels  by  this 
method,  sodium  carbonate  may  be  readily  procured  con- 
taining but  5  oW  of  silica. 

c.  To  a  clear  and  cold  solution  of  145  grams  of  sal 
soda  crystals  in  100  c.  c.  of  water,  add  gradually  with  vig- 
orous stirring  a  solution  of  60  parts  of  purified  oxalic  acid 
in  too  c.  c.  of  warm  water.  When  sodium  oxalate  ceases 
to  separate,  break  up  the  crystals,  and  transfer  them  to  a 
6-inch  filter  connected  with  the  Bunsen  filter  pump,  wash 
with  500  c.  c.  of  water  and  dry.  Heat  to  full  redness  in  a 
platinum  dish  until  the  oxalate  is  fully  decomposed,  dis- 
solve, filter,  and  evaporate  to  dryness.* 

Sodium  carbonate  must  be  perfectly  white.  Several 
grams  of  the  salt  must  dissolve  in  water  without  turbid- 
ity, and  if  the  salt  is  to  be  used  in  a  flux,  without  leav- 
ing grains  of  sand.  Its  solution,  after  supersaturation 
with  nitric  acid,  must  not  be  rendered  turbid  by  ba- 
rium chloride  or  silver  nitrate;  nor  must  addition  of  potas- 
sium sulphocyanate  impart  a  red,  or  warming  with 
ammonium  molybdate  and  nitric  acid  a  yellow  tint  to  it, 
or  give  a  yellow  precipitate ;  the  residue  which  remains 
upon  evaporating  its  solution  to  dryness,  after  previous 
supersaturation  with  hydrochloric  acid,  must  leave  no  resi- 
due (silica)  when  redissolved  in  water.  When  fused  in  a 
glass  tube  with  potassium  cyanide  for  a  long  time  in  a  cur- 
rent of  carbon  dioxide,  it  should  give  no  trace  of  a  dark 
sublimate  (arsenic). 

*  J.  LAWRENCE  SMITH. 


50  LABORATORY    MANUAL   OF 


POTASSIUM    CYANIDE.' 
KCN. 

Heat  potassium  ferrocyanide  of  commerce  (perfectly 
free  from  potassium  sulphate)  gently,  with  stirring, 
until  the  crystallization  water  is  completely  expelled ; 
triturate  the  anhydrous  mass,  and  mix  8  parts  of  the 
dry  powder  with  3  parts  of  perfectly  dry  potassium  car- 
bonate ;  fuse  the  mixture  in  a  covered  Hessian,  or,  bet- 
ter still,  in  a  covered  iron  crucible,  until  the  mass  is  in  a 
faint  glow,  appears  clear,  and  a  sample  of  it,  taken  out 
with  a  heated  glass  or  iron  rod,  looks  perfectly  white. 
Remove  the  crucible  now  from  the  fire,  tap  it  gently,  and 
let  it  cool  a  little  until  the  evolution  of  gas  has  ceased  ; 
pour  the  fused  potassium  cyanide  into  a  heated,  tall, 
crucible-shaped  vessel  of  clean  iron  or  silver,  or  into  a 
moderately  hot  Hessian  crucible,  with  proper  care,  to  pre- 
vent the  running-out  of  any  of  the  minute  particles  of  iron 
which  have  separated  in  the  process  of  fusion  and  have 
subsided  to  the  bottom  of  the  crucible.  Let  the  mass 
now  slowly  cool  in  a  somewhat  warm  place.  The  potas- 
sium cyanide  so  prepared  is  exceedingly  well  adapted  for 
analytical  purposes,  although  it  contains  potassium  car- 
bonate and  cyanite,  which  latter  is  upon  solution  in  water 
transformed  into  ammonium  carbonate  and  potassium  car- 
bonate (2CNOK  +  4H2O  =  K3CO3  +  (NH4)2CO3).  Keep 
it  in  the  solid  form  in  a  well-stoppered  bottle. 

Potassium  cyanide  must  be  of  a  milk-white  color 
and  quite  free  from  particles  of  iron  or  charcoal.  It 
must  completely  dissolve  in  water  to  a  clear  fluid.  It 


INORGANIC    PREPARATIONS.  51 

must  contain  neither  silica  nor  potassium  sulphide ;  the 
precipitate  which  lead  salts  produce  in  its  solution  must 
accordingly  be  of  a  white  color,  and  the  residue  which 
its  solution  leaves  upon  evaporation,  after  previous  super- 
saturation  with  hydrochloric  acid,  must  completely  dissolve 
in  water  to  a  clear  fluid. 


POTASSIUM    SULPHOCYANIDE., 
KCNS. 

Mix  together  46  parts  of  anhydrous  potassium 
ferrocyanide,  17  parts  of  potassium  carbonate,  and  32 
parts  of  sulphur;  introduce  the  mixture  into  an  iron 
pan  provided  with  a  lid,  and  fuse  over  a  gentle  fire; 
maintain  the  same  temperature  until  the  swelling  of  the 
mass  which  ensues  at  first  has  completely  subsided  and 
given  place  to  a  state  of  tranquil  and  clear  fusion  ;  in- 
crease the  temperature  now  towards  the  end  of  the  opera- 
tion, to  faint  redness,  in  order  to  decompose  the  potas- 
sium thiosulphate  which  has  been  formed  in  the  process. 
Remove  the  half- cooled  and  still  soft  mass  from  the 
pan,  crush  it,  and  boil  repeatedly  with  alcohol  of  from 
80  to  90  per  cent.  Upon  cooling,  part  of  the  potassium 
sulphocyanide  will  separate  in  colorless  crystals ;  to  obtain 
the  remainder,  distil  the  alcohol  from  the  mother  liquor. 

Solution  of  potassium  sulphocyanide  must  remain 
perfectly  colorless  when  mixed  with  perfectly  pure  dilute 
hydrochloric  acid. 


52  LABORATORY   MANUAL   OF 


HYDROGEN     SODIUM     SULPHITE. 
HNaSO3. 

Heat  5  parts  of  copper  tacks  or  clippings  with 
20  parts  of  concentrated  sulphuric  acid  in  a  flask, 
and  conduct  the  sulphur  dioxide  gas  evolved,  first 
through  a  washing  bottle  containing  some  water,  then 
into  a  flask  containing  7  parts  of  clean  crystallized  sal- 
soda,  and  from  20  to  30  parts  of  water,  and  which  is 
not  much  more  than  half  full ;  continue  the  transmission 
of  the  gas  until  the  evolution  of  carbon  dioxide  ceases. 
Keep  the  solution,  which  smells  strongly  of  sulphurous 
acid,  in  a  well-stoppered  bottle. 

Acid  sodium  sulphite,  when  evaporated  to  dryness 
with  pure  sulphuric  acid,  must  leave  a  residue,  the  aque- 
ous solution  of  which  is  not  altered  by  hydrogen  sulphide, 
nor  precipitated  yellow  by  heating  with  a  solution  of 
ammonium  molybdate  mixed  with  nitric  acid. 


POTASSIUM    NITRITE, 

KN02. 

In  an  iron  pan  fuse  I  part  of  nitre,  add  2  parts 
of  lead,  and  keep  stirred  with  an  iron  rod.  Even 
at  a  low  red  heat  the  lead  becomes  for  the  most 
part  oxidized  and  converted  into  a  yellow  powder  To 
oxidize  the  remainder,  the  heat  is  increased  to  visible 
redness  and  maintained  at  that  point  for  half  an  hour 
Allow  to  cool,  treat  with  cold  water,  filter  and  pass  car- 


INORGANIC    PREPARATIONS.  53 

bon  dioxide  through  the  filtrate.  This  precipitates  al- 
most the  whole  of  the  lead  in  solution,  the  remainder  is 
removed  with  a  little  hydrogen  sulphide.  Evaporate  the 
clear  fluid  to  dryness,  finally  with  stirring,  and  fuse  in 
order  to  destroy  any  potassium  thiosulphate. — (Aug. 
Stromeyer.)  When  required,  dissolve  I  part  in  2  parts 
of  water,  neutralize  cautiously  with  acetic  acid,  and  filter. 

Potassium   nitrite   must,    upon   addition  of  dilute  sul- 
phuric acid,  copiously  evolve  nitrogen  dioxide  gas. 


SODIUM    AND     POTASSIUM    NITRITE. 

A  very  sensitive  surface  of  spongy  platinum  is  ob- 
tained by  soaking  asbestos  yarn  in  a  solution  of  platinum 
oxalate,  made  by  heating  freshly  prepared  platinic  chloride 
at  204°  C.,  until  no  more  chlorine  is  evolved,  then  boiling 
the  residue  with  a  slight  excess  of  sodium  carbonate, 
finally  dissolving  it  in  oxalic  acid,  and  concentrating  the 
solution.  The  soaked  asbestos  yarn,  after  drying  and 
igniting,  is  exposed  to  a  current  of  ammonia  and  air  in  a 
combustion  tube,  the  remote  end  being  heated  by  a  Bun- 
sen  burner  to  start  the  reaction ;  the  whole  platinized  sur- 
face soon  becomes  intensely  hot,  while  dense  clouds  of 
ammonium  nitrite  rapidly  form,  and  are  conducted  into 
sodium  or  potassium  hydroxide,  where  the  corresponding 
nitrite  is  formed,  the  evolved  ammonia  being  used  for  pro- 
ducing a  further  supply  of  ammonium  nitrite.* 


By  H.   N.  WARREN,    (Chem.   News,  63,  294). 


54  LABORATORY   MANUAL   OF 


POTASSIUM    PYROANTIMONATE. 


Introduce  a  mixture  of  equal  parts  of  pulverized 
tartar-emetic  and  potassium  nitrate  in  small  portions 
at  a  time  into  a  red-hot  crucible.  After  the  mass 
has  deflagrated,  keep  it  at  a  moderate  red  heat  for  a  quar- 
ter of  an  hour  ;  it  froths  at  first,  but  after  some  time  it  will 
be  in  a  state  of  calm  fusion.  Remove  the  crucible  from 
the  fire,  let  the  mass  get  nearly  cold,  and  extract  it 
with  warm  water.  Transfer  to  a  suitable  vessel,  by  rinsing, 
and  decant  the  clear  fluid  from  the  heavy  white  powder 
deposited.  Concentrate  the  decanted  fluid  by  evaporation. 
After  one  or  two  days  a  doughy  mass  will  separate.  Treat 
this  mass  with  three  times  its  volume  of  cold  water,  work- 
ing it  at  the  same  time  with  a  spatula.  This  operation  will 
serve  to  convert  it  into  a  fine  granular  powder,  to  which 
add  the  powder  from  which  the  fluid  was  decanted,  wash 
well  with  boiling  water,  till  the  washings  cease  to  be  alka- 
line, and  dry  on  blotting  paper.  100  parts  of  tartar-emetic 
give  about  36  parts  of  the  pyroantimonate  Brunner). 


AMMONIUM     MOLYBDATE. 

CNH4)2Mo04, 
DISSOLVED  IN  NITRIC  ACID. 

MOLYBDIC  SOLUTION. 

Triturate  molybdenum  sulphide  with  about  an  equal 
bulk  of  coarse  quartz  sand  washed  with  hydrochloric 
acid,  until  it  is  reduced  to  a  moderately  fine  pow- 


INORGANIC    PREPARATIONS.  55 

der ;  heat  to  faint  redness,  with  repeated  stirring,  until 
the  mass  has  acquired  a  lemon-yellow  color  (which  after 
cooling  turns  whitish).  With  small  quantities  this  opera- 
tion may  be  conducted  in  a  flat  platinum  dish,  with  large 
quantities  in  a  muffle.  Extract  with  solution  of  ammonia, 
filter,  evaporate  the  filtrate,  heat  the  residue  to  faint  red- 
ness until  it  appears  yellow  or  white,  and  then  digest  for 
several  days  with  nitric  acid  in  the  water  bath,  in  order  to 
convert  any  phosphoric  acid  present  to  the  tribasic  state. 
When  the  nitric  acid  is  evaporated  dissolve  the  residue  in 
4  parts  of  solution  of  ammonia,  filter  rapidly,  and  pour  the 
filtrate  into  15  parts  by  weight  of  nitric  acid  of  1.20  specific 
gravity.  Keep  the  mixture  standing  several  days  in  a 
moderately  warm  place,  which  will  cause  the  separation  of 
any  remaining  traces  of  phosphoric  acid  as  ammonium 
phosphomolybdate.  Decant  the  colorless  fluid  from  the 
precipitate,  and  keep  it  for  use.  Heated  to  40°  C.  no  white 
precipitate  (molybdic  acid  or  an  acid  salt  of  the  same)  will 
separate  ;  but  above  that  point  precipitation  will  take  place 
unless  more  nitric  acid  be  added  (Eggertz). 


AMMONIUM    CHLORIDE. 

NH4C1. 

Select  sublimed  white  sal  ammoniac  of  commerce. 
If  it  contains  iron  it  must  be  purified  by  slowly  pass- 
ing chlorine  gas  into  the  nearly  saturated  solution  for  a 
short  time  or  until  potassium  ferricyanide  gives  no  blue 
color  with  a  few  drops  of  the  liquid.  Ammonia  is  then 
added  in  slight  excess,  the  whole  is  warmed,  filtered  from 
the  separated  ferric  oxide  and  evaporated  to  crystallization. 


56  LABORATORY    MANUAL   OF 

Solution  of  Ammonium  Chloride  must  leave  no  fixed 
residue  upon  evaporation  on  platinum,  and  ammonium 
sulphide  must  have  no  action  upon  it.  Its  reaction  must 
be  perfectly  neutral. 


SODIUM    NITRATE. 

NaNO3. 

Neutralize  pure  nitric  acid  with  pure  sodium  car- 
bonate exactly,  and  evaporate  to  crystallization.  Dry  the 
crystals  thoroughly,  triturate  and  keep  the  powder  for  use. 
A  solution  of  sodium  nitrate  must  not  be  made  turbid 
by  solution  of  silver  nitrate  or  barium  nitrate,  nor  precipi- 
tated by  sodium  carbonate. 


MONO    SODIUM    PHOSPHITE. 

2NaHP03  +  5H30. 

Is  obtained  by  adding  sodium  hydroxide  or  carbonate 
to  phosphorous  acid  until  the  solution  is  neutral  to  methyl 
orange.  The  liquid  is  then  concentrated  by  evaporation 
and  the  salt  crystallizes.  Not  unfrequently  a  supersatur- 
ated solution  is  obtained,  which  crystallizes  in  contact 
with  a  fragment  of  the  solid  phosphite.  If  no  crystals  of 
the  phosphite  are  at  hand,  the  solution  is  concentrated  un- 
til it  has  the  composition  of  the  crystals  and  is  cooled  to  a 
low  temperature.  The  salt  is  recrystallized  from  water 
and  dried  by  exposure  to  air.  It  can  also  be  obtained  by 
the  action  of  phosphorus  trichloride  on  sodium  carbonate, 
but  the  separation  of  the  sodium  chloride  is  difficult. 


INORGANIC    PREPARATIONS.  57 

Monosodium  phosphite  is  very  soluble  in  water  and  melts 
at  42°  C.  At  100°  C.  the  fused  salt  loses  water  and  the 
liquid  deposits  crystals  which  may  be  either  a  lower 
hydrate  or  the  anhydrous  salt.  If  heated  at  IOOQ  C.  for 
a  long  time,  it  becomes  completely  dehydrated  ;  it  also 
becomes  anhydrous  in  a  dry  vacuum.  When  heated 
above  130^  C.  the  phosphite  changes  into  sodium  pyro- 
phosphite. 

Potassium  phosphite  is  obtained  in  a  similar  manner. 
It  forms  anhydrous  crystals,  which  are  difficult  to  purify  by 
recrystallization. 


POTASSIUM     CHLORATE. 
KC1O3. 

100  grams  potassium  carbonate  are  dissolved  in  warm 
water  in  a  small  flask  heated  to  boiling,  and  chlorine  is 
conducted  through  the  liquid  until  it  is  no  longer  alkaline. 
Then  dilute  with  hot  water  up  to  a  volume  of  350  c.  c.,  fil- 
ter and  let  it  crystallize. 

As  a  test  a  weighed  sample  of  the  dried  salt  put  in  a 
covered  platinum  dish  is  heated  first  on  the  gas  furnace, 
then  on  the  Bunsen  burner  with  a  small  flame  to  incipient 
redness;  the  uncovering  of  the  hot  dish  must  be  avoided. 


The  potassium  chloride  remains  in  the  mother  liquor.  On 
heating  the  potassium  chlorate,  the  perchlorate  first  forms, 
then  the  chloride  and  this  finally  volatilizes  at  red  heat. 


58  LABORATORY    MANUAL    OF 


POTASSIUM    BISULPHATE. 
KHSO4. 

Mix  7  parts  of  pure  sodium  sulphate  (obtained  by 
recrystallization  of  clean  Glauber's  salts,  and  drying  away 
the  water  of  crystallization  at  a  gentle  heat)  with  5  parts 
of  pure  concentrated  sulphuric  acid,  in  a  platinum  dish  or 
large  platinum  crucible,  heat  to  low  redness  till  the  mass 
is  in  a  state  of  calm  fusion,  then  pour  out  into  a  platinum 
dish  placed  in  cold  water,  or  upon  a  piece  of  porcelain, 
break  the  cake  into  smaller  pieces  and  keep  for  use. 

The  sodium  disulphate  must  dissolve  in  water  with 
ease  to  a  clear  fluid  with  a  strong  acid  reaction.  The 
solution  must  not  be  rendered  turbid  or  precipitated  by 
hydrogen  sulphide  or  by  ammonia  and  ammonium  sul- 
phide. 


HYDROGEN  SODIUM  AMMONIUM  PHOSPHATE. 
NaHNH4PO4. 

a.  Heat    to    boiling    6    parts    of    hydrogen    disodium 
phosphate  and  I  part  of  pure  ammonium   chloride  with  2 
parts  of  water,  and   let  the  solution  cool.      Free  the  crys- 
tals produced,  from  the  sodium   chloride  which  adheres   to 
them,  by  recrystallization,  with  addition  of  some  solution 
of  ammonia.      Dry  the  purified  crystals,  pulverize  and  keep 
for  use. 

b.  Take  2  equal  parts  of  pure  tribasic  phosphoric  acid, 
and  add  solution  of  soda    to  the  one,  solution  of  ammonia 


INORGANIC    PREPARATIONS.  59 

to  the  other,  until  both  fluids  have  a  distinct  alkaline  reac- 
tion ;  mix  the  two  together,  and  let  the  mixture  crystal- 
lize. 

Hydrogen  sodium  ammonium  phosphate  dissolves 
in  water  to  a  fluid  with  feebly  alkaline  reaction.  The 
yellow  precipitate  produced  in  this  fluid  by  silver  ni- 
trate must  completely  dissolve  in  nitric  acid.  Upon  fusion 
on  a  platinum  wire,  microcosmic  salt  must  give  a  clear  and 
colorless  bead. 


POTASSIUM     FERRICYANIDE. 


Conduct  chlorine  gas  slowly  into  a  solution  of  I  part 
of  potassium  ferrocyanide  in  10  parts  of  water,  with 
frequent  stirring,  until  the  solution  exhibits  a  fine  deep 
red  color  by  transmitted  light  (the  light  of  a  candle 
answers  best),  and  a  portion  of  the  fluid  produces  no 
longer  a  blue  precipitate  in  a  solution  of  ferric  chloride, 
but  imparts  a  brownish  tint  to  it.  Evaporate  the  fluid  now 
in  a  dish  to  y£  of  its  weight,  and  let  crystallize.  The 
mother  liquor  will  upon  further  evaporation  yield  a  second 
crop  of  crystals  equally  fit  for  use  as  the  first.  Dissolve 
the  whole  of  the  crystals  obtained  in  3  parts  of  water,  filter 
if  necessary  ;  evaporate  the  solution  briskly  to  half  its  vol- 
ume, and  let  crystallize  again.  The  solution,  as  already 
remarked,  must  produce  neither  a  blue  precipitate  nor  a 
blue  color  in  a  solution  of  ferric  chloride.  As  this  salt  de- 
composes when  long  kept  in  solution,  it  is  best  preserved 
and  applied  in  the  state  of  powder. 


60  LABORATORY    MANUAL   OF 


POTASSIUM    IODIDE. 
K.I. 

6  grams  pure  iron  powder  are  suspended  in  a  small  flask 
with  50  c.  c.  water,  25  grams  iodine  are  gradually  added, 
keeping  the  mixture  cold.  At  the  end  of  the  reaction  there 
must  still  be  present  a  slight  excess  of  iron.  The  solution 
is  filtered  off  from  the  residue,  washed  with  a  little  water, 
and  5  grams  iodine  added  to  the  filtrate.  Now  16.5  grams 
potassium  carbonate  are  dissolved  in  a  porcelain  dish  with 
50  c.  c.  hot  water,  and  the  ferrous  iodide  solution  added  to 
this  boiling  mixture.  Ferrous  hydrate  separates  and  car- 
bonic acid  is  freely  evolved  ;  filter  and  evaporate  to  crystall- 
ization. 

By  the  above  process  a  mixture  of  ferrous  and  ferric 
iodides  is  formed,  and  this  by  decomposition  with  alkali 
yields  ferrous  oxide,  which  is  readily  removed  by  filtration. 

The  potassium  iodide  in  sulphuric  acid  solution  must 
not  turn  starched  paper  blue,  and  must  be  free  from 
bromine  and  chlorine. 


POTASSIUM     CYANATE. 

KCNO. 

Commercial  potassium  ferrocyanide  is  broken  in  pieces, 
dehydrated  in  an  iron  dish  on  a  gas  furnace  and  finely 
powdered.  200  grams  of  the  anhydrous  salt  are  thor- 
oughly mixed  with  150  grams  potassium  dichromate  which 
has  been  freed  from  adhering  moisture  by  fusing  on  the 


INORGANIC    PREPARATIONS.  6 1 

gas  stove.  The  mixture  is  placed  into  a  capacious  iron 
dish  in  portions  by  means  of  a  spoon,  and  heated  to  such 
an  extent  over  a  Bunsen  burner  or  gas  stove  that  every 
portion  of  the  powder  added  is  converted  into  a  black 
mass.  Stir  with  an  iron  spatula  while  putting  the  mixture 
into  the  dish.  The  temperature  must  not  rise  high  enough 
to  cause  fusion  of  the  mass.  After  cooling,  the  porous 
mass  is  powdered,  put  into  a  flask  with  I  litre  of  8(D% 
boiling  alcohol,  shaken  and  boiled  for  five  minutes, 
with  reversed  condenser.  After  settling,  pour  off  the  clear 
solution  into  a  beaker,  which  is  set  in  cold  water  to  cool, 
whereupon  the  potassium  cyanate,  especially  by  stirring 
with  a  glass  rod,  precipitates  in  a  heavy  white  crystallized 
powder.  The  mother  liquor  serves  for  further  (3d  or  4th) 
extraction  of  the  black  product. 

K4Fe(CN)6  +  2K3Cr2O7  =  6KCNO  +  2Cr3O3  +  FeO  +  K2O. 

The  unaltered  potassium  ferrocyanide  remains  in- 
soluble on  recrystallization  from  alcohol.  The  hot 
solutions  must  be  cooled  quickly,  as  by  heating  any  length 
of  time,  the  water  contained  in  the  diluted  alcohol  would 
decompose  the  cyanate. 

KCNO  f  2H3O  =  K(NH4)CO3. 

Analyze  the  salt  by  evaporating  a  sample  with  cone, 
sulphuric  acid  and  fusing  the  remaining  potassium  sul- 
phate with  addition  of  a  grain  of  ammonium  carbonate.* 


*  C.  A.  BELL,  Chem.  News,  32,  99. 


62  LABORATORY    MANUAL   OF 


POTASSIUM     COBALTIC     OXALATE. 


Is  obtained  by  mixing  cobaltic  hydroxide,  potassium 
oxalate,  oxalic  acid  and  water  to  a  thick  paste,  and  allow- 
ing the  mixture  to  stand  from  I4to2i  days.  After  recrystall- 
ization,  the  salt  is  obtained  in  nearly  black,  well-formed, 
seemingly  monosymmetric  crystals,  which  in  thin  lamellae 
show  distinct  dichroism  (dark-blue  and  emerald-green).* 

When  treated  with  cold  saturated  sodium  chloride  solu- 
tion, the  sodium  potassium  salt  is  obtained,  crystallizing  in 
beautiful  pyramids. 


POTASSIUM     METANTIMONATE. 

K4Sb2O7. 

IOO  grams  of  black  sulphide  of  antimony,  150  grams  of 
potassium  carbonate,  IOO  grams  of  slaked,  lime  and  20 
grams  of  sulphur,  are  shaken  with  12  liters  of  water  and 
after  standing  eight  days  the  mixture  is  filtered.  The  fil- 
trate, which  contains  potassium  sulphantimonate,  is  boiled 
with  1 20  grams  of  copper  oxide  and  filtered.  The  filtrate 
is  diluted  with  water  and  treated  with  carbonic  anhydride, 
when  potassium  metantimonate  is  precipitated. t 


*  F.  KEHRMANN,  Ber.,  19,  3101. 

f  DUYK,  Bull.  Soc.  Roy.  Pharm.,  Bruxelles,  37,  109. 


INORGANIC    PREPARATIONS.  63 

CRYSTALLINE    NORMAL   LITHIUM    PHOS- 
PHATE   AND    ARSENATE. 

Fused  lithium  chloride  dissolves  the  amorphous,  normal 
phosphate,  and  on  cooling  and  washing  the  melted  mass, 
rhomboidal,  tabular  crystals  of  normal  lithium  phosphate, 
which  have  a  sp.  gr.  2.41  at  15°  C.,  and  are  infusible  at  a 
white  heat,  are  obtained.  The  normal  arsenate  is  similarly 
prepared  ;  it  corresponds  with  the  phosphate  physically, 
and  is  of  sp.  gr.  3.07  at  15°  C.* 


PREPARATION    OF     PURE    CAESIUM    AND 
RUBIDIUM     COMPOUNDS 

The  preparation  of  pure  caesium  rubidium  salts  from 
their  minerals  is  carried  out  as  follows :  They  are  first 
separated  in  the  form  of  the  double  salts  with  lead  tetra- 
chloride ;  the  latter  is  decomposed  with  water,  the  solu- 
tion treated  with  a  slight  excess  of  ammonium  sulphide  to 
free  it  from  lead,  and  the  filtrate  evaporated  to  dryness ; 
the  mixed  chlorides  of  caesium  and  rubidium  are  dissolved 
in  concentrated  nitric  acid,  the  solution  evaporated  to  dry- 
ness,  the  residue  dissolved  in  water,  excess  of  oxalic  acid 
added,  and  the  mixture  again  evaporated  to  dryness,  and 
heated  in  a  platinum  crucible  until  the  oxalates  are  com- 
pletely converted  into  carbonates.  The  rubidium  is  then 
separated  as  acid  oxalate  and  the  caesium  as  caesium  anti- 
mony chloride,  t 


*  By  A.  DE  SHULTEN,  Bull.  Soc.  Chim.  [3],  i,  479. 
t  By  H.  L.  WELLS,  AMER.  J.  Sci.,  46,  186. 


64  LABORATORY    MANUAL   OF 


PREPARATION    OF    PURE    RUBIDIUM    SALTS. 

Commercial  "  pure  "  rubidium  salts  contain  small  quan- 
tities of  caesium  and  potassium,  which  it  is  difficult  to  detect 
by  means  of  the  spectroscope.  To  obtain  a  pure  salt,  com- 
mercial rubidium  chloride  (30  grams)  is  dissolved  in  very 
strong  hydrochloric  acid  (250  c.  c.)  and  antimony  chloride 
(2.5  grams)  dissolved  in  strong  hydrochloric  acid  is  added. 
The  small  precipitate  (about  1.4  grams  Rb,  SbCl4  and 
CsSbCl4)  is  filtered  off  on  an  asbestos  filter,  the  filtrate 
evaporated  almost  to  dryness,  the  antimony  still  present 
removed  with  hydrogen  sulphide,  and  the  resulting  mix- 
ture dissolved  in  strong  hydrochloric  acid.  Rather  more 
of  a  hydrochloric  acid  solution  of  stannic  chloride  is  added 
than  is  necessary  to  form  the  stannic  chloride,  Rb3SnCl6 ; 
this  substance  is  then  precipitated,  whilst  potassium  stannic 
chloride,  K2SnCl6,  remains  in  solution.  The  precipitate  is 
allowed  to  settle,  washed  several  times  by  decantation,  col- 
lected on  an  asbestos  filter,  dissolved  in  water,  and  the  tin 
removed  with  hydrogen  sulphide.  The  rubidium  chloride 
so  obtained  is  pure,  0.44  gram  contains  29.30  instead  of 
29.34  per  cent,  of  chlorine.* 


PREPARATION     OF     TUNGSTATES     FREE 
FROM     MOLYBDENUM. 

Commercial  tungstates  and  tungstic  acid  contain  vary- 
ing quantities  of  molybdenum.  After  several  unsuccessful 
attempts  to  get  rid  of  this  impurity,  the  following  method 

*  By  W.  MUTHMANN,  Ber.  26,  1019-1020. 


INORGANIC    PREPARATIONS.  65 

was  found  to  give  the  desired  result  Sodium  tungstate, 
prepared  in  the  usual  way,  is  dissolved  in  cold  water,  and 
to  the  saturated  solution  hydrochloric  acid  is  added  until 
the  reaction  is  only  feebly  alkaline  ;  the  paratungstate  thus 
obtained  is  crystallized  out  and  once  recrystallized.  One- 
half  of  it  is  dissolved  in  boiling  water,  and  hydrochloric 
and  a  little  nitric  acid  added ;  hydrated  tungstic  acid  is 
precipitated.  This  is  washed  thoroughly  with  hot  water 
and  added  to  a  boiling  solution  of  the  other  half  of  the 
paratungstate,  until  a  portion  no  longer  gives  a  precipi- 
tate with  hydrochloric  acid.  The  bulk  of  the  solution  is 
then  filtered,  hydrochloric  acid  is  added,  and  the  solution 
is  boiled  and  repeatedly  saturated  with  hydrogen  sulphide. 
This  precipitates  the  molybdeum  as  sulphide,  whilst  the 
metatungstate  is  not  attacked.  The  solution  is  filtered, 
concentrated,  oxidized  with  a  few  drops  of  bromine  water, 
and  neutralized  with  soda ;  pure  sodium  paratungstate 
can  then  be  obtained  from  it  by  crystallization.  To  ob- 
tain the  potassium  and  ammonium  salts,  the  acid  should  be 
prepared  by  adding  hydrochloric  acid  to  the  sodium  salt, 
and  then  neutralize  with  potash  or  ammonia. 

An  analysis  of  sodium  paratungstate  thus  prepared 
agreed  better  with  the  formula  5Na2O,  12WO3,  28H2O 
than  with  3Na2O.  7WO3,  16H2O.* 


TITANIUM    TRIOXIDE. 
Ti08. 

Pure  titanium  chloride  is  added  drop  by  drop  to  dilute 
alcohol,  and   the   clear  and  very  dilute   solution  is  treated 


*  By  C.   FRIEDHEIM  and  R.  MEYER,  Zeit.  Anorg.  Chem.  i,  76-81. 

5 


66  LABORATORY    MANUAL   OF 

with  a  large  excess  of  hydrogen  peroxide.  Ammonia,  am- 
monium carbonate,  or  aqueous  potash,  is  added  to  the 
solution  with  the  production  of  a  yellow,  or  in  case  of 
ammonia,  of  a  reddish  yellow  liquid,  which  after  some  time 
yields  a  yellow  precipitate.  This  is  allowed  to  subside, 
the  clear  solution  siphoned  off,  and  the  precipitate  repeat- 
edly washed  by  decantation ;  the  compound,  however, 
tends  to  retain  water  and  salts  in  considerable  quantities. 
When  dried  on  a  tile  it  approximates  to  the  composition  : 

TiO3  +  3H2O.* 


PREPARATION    OF    VANADYL    TRICHLORIDE. 

EXTRACTION  OF  VANADIUM  FROM  ITS  ORES. 

For  the  extraction  of  vanadium  from  its  ores  advantage 
is  taken  of  the  volatility  of  vanadyl  trichloride.  The 
finely  divided  mineral  is  intimately  mixed  with  about 
one  quarter  of  its  weight  of  lamp  black  and  a  little  oil,  and 
ignited  to  volatilize  the  arsenic  and  zinc.  The  calcined 
product  is  then  slowly  heated  to  131°  C.  in  a  stream  of  dry 
chlorine,  and  the  vanadyl  trichloride  collected  in  tubes  im_ 
mersed  in  a  freezing  mixture.  When  it  is  desired  to 
determine  the  quantity  of  vanadium  in  an  ore,  the  above 
method  is  employed,  and  the  vanadyl  trichloride  is  col- 
lected in  a  series  of  bulbs  containing  distilled  water ;  the 
vanadic  acid  is  then  reduced  with  zinc,  and  estimated  volu- 
metrically  with  the  aid  of  potassium  permanganate.! 


*  A.  CLASSEN,  Ber.  21,  370. 

f   By  L.   L'HOTE    Ann.   Chim.   Phys.   [6],  22,  407-412. 


INORGANIC    PREPARATIONS.  67 

X^C^^X 


VANADYL    CHLORH^iC^ 

Prepared  from  vanadianite  (14.42%  V2O5)  by  mixing 
the  powdered  mineral  with  four  times  its  weight  of  lamp 
black,  making  into  a  paste  with  oil  and  calcining.  The 
calcined  product  is  then  heated  in  an  oil  bath  in  a  current 
of  dry  chlorine,  care  being  taken  to  prevent  the  tempera- 
ture exceeding  131°  C.  Pure  vanadyl  chloride  begins  to 
distill  at  98°  C.,  and  if  the  temperature  is  raised  to  131  °C. 
the  whole  of  the  vanadium  in  the  mineral  is  converted  into 
this  compound.* 


AMMONIUM    BICARBONATE. 
(NH4)HC03. 

Pour  cone,  aqua  ammonia  into  a  small  flask  and  close 
it  with  a  stopper  attached  to  a  short  glass  tube,  through 
which  carbonic  acid  is  passed.  The  neutral  ammonium  car- 
bonate which  precipitates  at  first,  redissolves,  and  after  the 
liquid  has  for  a  time  been  subjected  to  the  carbonic  acid, 
the  acid  salt  separates.  More  bicarbonate  may  be  obtained 
from  the  mother  liquor  by  mixing  it  with  alcohol.  It  is 
preserved  in  glass  tubes  which  are  filled  with  carbonic  acid 
and  sealed. 

Ammonium  bicarbonate  crystallizes  in  hard,  glossy, 
rhombic  prisms,  very  readily  volatile.  The  aqueous  solu- 
tion must  not  be  rendered  turbid  by  the  addition  of 
calcium  chloride. 


*  BY  L.   L'HoTE,   Compt.    Rend.    101-1151. 


68  LABORATORY    MANUAL    OF 


AMMONIUM    BROMIDE. 
NH4Br. 

AND 

POTASSIUM    BROMIDE. 
KBr. 

From  a  dropping  funnel  with  a  finely  drawn  out  stem 
75  c.  c.  of  bromine  are  allowed  to  flow,  slowly  and  with  con- 
tinual shaking,  into  220  c.  c.  of  cone.  (30%)  ammonia  con- 
tained in  a  flask  cooled  with  ice-water,  taking  care  that  the 
liquid  shall  remain  strongly  ammoniacal  at  the  end  of  the 
reaction.  It  is  then  boiled  until  the  free  ammonia  has 
been  driven  out  and  evaporated  to  crystallization.  The 
ammonium  bromide  is  dried  by  gently  heating  in  a  porce- 
lain dish  over  an  open  fire.  196  grams  ammonium  bro- 
mide are  dissolved  in  hot  water,  200  grams  potassium 
bicarbonate  added,  and  the  whole  is  heated  to  boiling; 
when  the  ammonia  has  been  driven  out  it  is  allowed 
to  crystallize  : 

4NH3+3Br=3NH4Br+N. 

If  the  solution  should  become  acid,  or  the  bromine 
flow  in  too  rapidly,  there  might  be  a  formation  of  nitrogen 
bromide  which  would  cause  an  explosion. 

As  a  test  a  small  sample  of  the  salt  is  boiled  in  a  re- 
tort with  a  large  excess  of  iron-ammonia  alum  in  aqueous 
solution,  whereby  any  iodine  which  may  be  present  will 
pass  over  in  a  free  state  ;  remove  the  bromine  from  the 
residue  by  addition  of  potassium  permanganate  solution 
and  test  for  chlorine.  This  separation  of  the  halo- 


INORGANIC    PREPARATIONS.  69 

genes   depends  on   the   fact   that   ferric   salts  will  set  free 
iodine  from  neutral  solutions  of  the  iodides  : 

Fe3(S04)3  +  2KI  =  2FeS04  4-  K3SO4  +  21. 
while  the  bromides  remain  unchanged. 

On  the  other  hand,  these  are  also  entirely  decomposed 
if  a  small  quantity  of  a  strong  oxydizing  agent  (perman- 
ganate) is  present.  The  chlorides  resist  the  simultaneous 
influence  of  these  two  agents. 


PREPARATION  OF  AMMONIUM  PERSULPHATE. 

A  porous  clay  cell  (80  to  100  c.  c.  capacity),  containing 
a  saturated  solution  of  ammonium  sulphate  in  a  mixture 
of  i  part  by  volume  of  sulphuric  acid  with  8  parts  by 
volume  of  water  is  placed  in  a  beaker  and  surrounded  by 
a  mixture  of  equal  volumes  of  sulphuric  acid  and  water. 
A  lead  cylinder,  placed  round  the  porous  cell,  serves  as 
the  carthode  and  a  platinum  spiral,  having  a  surface  of  0.5 
sq.  cen.,  is  suspended  inside  the  porous  cell  to  serve  as  the 
anode.  The  beaker  is  embedded  in  ice.  The  electrolysis 
is  effected  by  a  current  of  2  to  3  amperes  ;  some  8  volts  will 
be  necessary  when  the  internal  resistance  of  the  decom- 
posing cell  is  about  I  ohm.  After  2  to  3  hours  the  contents 
of  the  porous  cell  are  filtered  through  glasswool  and  the 
crystals  of  ammonium  persulphate  dried  on  a  porous 
plate  ;  the  filtrate  is  shaken  with  ammonium  sulphate  and 
once  more  electrolysed.  20  to  40  grains  of  the  persulphate 
may  thus  be  obtained  in  one  operation,  the  yield  being 
least  at  the  outset,  when  the  liquor  is  being  saturated 


70  LABORATORY    MANUAL   OF 

with  the  persulphate.  The  sulphuric  acid  in  the  outer 
cell  eventually  becomes  alkaline  from  the  transit  of  the 
ammonium,  and  pari  passu  the  ammonium  sulphate 
in  the  inner  cell  becomes  strongly  acid  ;  from  time  to 
time  the  former  liquid  must  be  renewed  and  the  latter 
nearly  neutralized  with  ammonia.  To  recover  the  per- 
sulphate left  in  the  liquor  when  the  preparation  has  been 
completed  a  concentrated  solution  of  potassium  carbonate 
or  acetate  is  added ;  potassium  persulphate  will  thus  be 
precipitated,  as  100  parts  of  water  only  dissolve  2  parts  of 
this  salt,  whereas  they  dissolve  65  parts  of  the  ammonium 
salt* 

Ammonium  persulphate  thus  prepared  contains  some 
3  to  5  per  cent,  of  impurities,  consisting  chiefly  of  ammo- 
nium sulphate,  but  partly  of  ammonium  alum,  derived 
from  the  clay  of  the  porous  cell.  It  may  be  recrystallized 
from  water. 


AMMONIUM    BICHROMATE, 
(NH4)3Cr207. 

Chrome  iron  ore  is  heated  with  sodium  or  potassium 
salts  ;  the  resulting  monochromate  is  dissolved  in  water, 
treated  with  2  equivalents  of  acids,  and  then  neu- 
trallized  with  ammonia  or  ammonium  carbonate.  The 
solution  containing  a  dichromate  and  sulphate,  chloride, 
or  nitrate,  as  the  case  may  be,  is  concentrated  ;  the  latter 
salts  as  they  crystallize  are  removed,  and  finally  on  cool- 


*  By  K.  ELBS,  J.  pr.  Chem.  [2]  48,  185-189. 


INORGANIC   PREPARATIONS.  71 

ing  ammonium  dichromate  crystallizes  out.  The  potas- 
sium or  sodium  salts  are  used  again  for  heating  with  fresh 
chrome  iron  ore.* 


AMMONIUM    NITRATE. 
NH4NO3. 

The  mixture  of  nitrogen  oxides  evolved  during  the 
action  of  arsenious  anhydride  or  nitric  'acid  is  passed  over 
coarsely  powdered  ammonium  carbonate  kept  cool  by 
ice.  The  half  liquid  mass  is  treated  with  alcohol,  the  un- 
changed carbonate  filtered  off,  and  the  ammonium  nitrate 
precipitated  by  means  of  ether.  The  nitrate  so  obtained 
is  of  90  to  94  per  cent,  purity,  and  may  be  purified  by 
resolution  in  96  per  cent,  alcohol  and  reprecipitation 
with  ether.  Pure  ammonium  nitrate  forms  almost  color- 
less needles,  which  are  deliquescent  and  dissolve  in  water 
with  development  of  heat.  It  is  easily  but  slowly  soluble 
in  alcohol,  and  is  precipitated  from  this  solution  by  ether, 
chloroform  or  ethylic  acetate.  Concentrated  solutions  ap- 
pear to  decompose  with  explosive  violence  at  60°  to  70°  C., 
like  the  solid  salt,  and  in  acid  solutions,  such  decomposi- 
tion sometimes  occurs  at  ordinary  temperatures.  The  dry 
salt  may  be  safely  kept  in  an  atmosphere  of  hydrogen  and 
in  presence  of  pieces  of  ammonium  carbonate  and  of  lime. 
It  is  best  kept  and  transported  under  absolutely  dry  and 
alcohol  free  ether,  t 


*  T.  J.  HOOD,  Chem.  Zeit.  n,  55. 

f   S.  P.  L.  SORENSEN,  Zeit.  anorg.  Chem.,  7,  33. 


72  LABORATORY    MANUAL   OF 


AMMONIUM    DI    HYDROGEN   PHOSPHITE. 


A  solution  of  phosphorous  acid  mixed  with  ammonia 
until  neutral  to  methyl  orange,  and  then  concentrated 
until  the  weight  of  the  liquid  is  one-fourth  or  one-fifth 
more  than  the  calculated  weight  of  the  salt,  yields  large 
deliquescent  crystals,  which  can  be  dried  over  sulphuric 
acid  or  at  100°  C.  Similar  crystals  are  obtained  if  the 
liquid  is  concentrated  in  vacuo  at  ordinary  temperature. 
The  crystals  have  the  composition  NH^gPOs,  a°d  seem 
to  be  monoclinic  prisms;  they  melt  at  123°  C.  and  are 
very  soluble  in  water.  At  145°  C.  they  lose  half  their 
ammonia  without  evolution  of  hydrogen  phosphide  and 
yield  a  gummy  mass  which  seems  to  contain  crystals. 
At  a  higher  temperature  ammonia  and  hydrogen  phos- 
phide are  given  off  and  phosphoric  acid  is  formed.* 


AMMONIO  ZINC  CHLORIDES. 

If  a  stream  of  ammonia  is  passed  into  a  hot  concen- 
trated solution  of  zinc  chloride  until  the  precipitate  first 
formed  is  redissolved,  and  the  whole  is  then  allowed  to 
cool,  nacreous  scales  of  the  composition  ZnCl2,  4NH3+  H3O 
crystallize  out.  On  concentration  the  mother  liquor  yields 
crystals  of  the  formula  ZnCl2,  2NH3;  this  compound 
separates  in  colorless  rhombic  crystals,  which  do  not 


*  L.  Amat.  Compt.  Rend.,  105,  809. 


INORGANIC   PREPARATIONS.  73 

change  on  exposure  to  air.  It  is  insoluble  in  water,  but 
when  boiled  with  it  decomposes  with  evolution  of  am- 
monia. It  is  easily  soluble  in  solutions  of  ammonia  or 
ammonium  chloride.  The  same  compound  is  also  formed 
when  ammonia  is  added  to  a  cold  dilute  solution  of  zinc 
chloride  until  the  precipitate  first  formed  is  redissolved,  or 
when  freshly  precipitated  zinc  hydroxide  is  dissolved  in 
a  concentrated  solution  of  ammonium  chloride.  The  same 
compounds,  in  well  formed  crystals,  has  also  been  found 
in  Leclanche  cells.  The  constitution  is  probably  expressed 
by  the  formula  NH8Cl.Zn.NH8Cl.* 


CUPROUS    CHLORIDE. 
CuoCte. 

Cuprous  Chloride  can  be  conveniently  prepared  by 
heating  a  mixture  of  copper  sulphate  (4  grams)  and  so- 
dium hypophosphite  (2  grams)  in  about  50  c.  c.  of 
water  to  which  30  drops  of  fuming  hydrochloric  acid  are 
added. 

The  cuprous  chloride  is  deposited  and  can  be  purified 
in  the  ordinary  way.  The  change  can  be  explained  thus  : 
Copper  hypophosphite  is  at  first  formed,  and  this  is  con- 
verted by  the  hydrochloric  acid  into  cuprous  chloride  and 
phosphoric  acid.  The  equation  is  as  follows  :  2CuCl2  -f 
H3PO2  +  H2O  =  H3PO3  +  2HC1  +  Cu3Cl2. 

Another  method  of  preparation  is  to  pour  100  c.  c. 
hot  water  over  42  grams  copper  chloride  (cryst.)  and 
32  grams  metallic  copper  (granulated  or  turnings)  ;  add 

lBft^px. 
.  THOMAS,  Be,,  2o,  743. 

J 

W-.^^S 


74  LABORATORY  MANUAL  oP 

200  c.  c.  crude  hydrochloric  acid  (sp.  gr.  1.175),  and  boil 
gently  in  a  flask  closed  by  a  small  funnel ;  finally  add  a 
little  fuming  hydrochloric  acid  and  boil  until  the  solution 
becomes  colorless.  This  operation  lasts  one  to  two  hours, 
but  can  be  hastened  considerably  if  the  copper  powder  in 
cakes  obtained  in  preparing  blue  vitriol  is  added  to  the 
solution.  The  colorless  solution  is  poured  off  from  the 
surplus  copper  into,  a  cylinder  filled  with  cold  distilled 
water,  the  cheesy  precipitated  protochloride  is  allowed  to 
settle  and  decanted  immediately,  quickly  filtered,  washed 
with  ether  and  alcohol,  and  dried  in  vacuum  over  sul- 
phuric acid. 

CuCl3  +  Cu  =  Cu2Cl2.* 

Cuprous  chloride  forms  in  heavy  white  masses,  insolu- 
ble in  water,  and  oxydizes  easily  in  the  air  and,  with 
chlorine  water  or  aqua  regia  (nitromuriatic  acid),  dissolve 
readily  as  copper  chloride.  By  heating  in  small  tubes 
the  protochloride  melts  without  decomposition. 


CUPROUS    CYANIDE. 

(CugCN).,. 

50  grams  crystallized  blue  vitriol  are  dissolved  in  300 
c.  c.  hot  water,  and  to  this  hot  solution  in  a  flask,  add, 
by  means  of  a  dropping  funnel,  a  solution  of  26  grams 
potassium  cyanide  in  50  c.  c.  water.  The  escaping  cy- 
anogen gas  is  passed  through  a  glass  tube  bent  upward, 
tapering  to  a  point  and  lighted  at  the  end  of  the  tube  as 
soon  as  the  apparatus  is  filled  with  it.  The  gas  is  very 


By  A  CAVAZZI,  Gazzetta  16,  167-168). 


INORGANIC    PREPARATIONS.  75 

poisonous  and  burning  is  a  ready  way  of  getting  rid  of  it. 
The  white  cheesy  sediment  is  separated  by  decanting  from 
the  faintly  bluish-colored  solution,  washed  with  water  and 
dried  on  an  earthen  plate. 

CuSO4  f  2KCN  =  Cu(CN)3  -f  K3SO4. 

2Cu(CN)3  =  Cu3(CN)3  +  CN3. 

Cuprous  chloride  is  a  tolerably  stable  white  powder, 
similar  on  the  whole  to  the  copper  protochloride.  Decom- 
poses by  heating,  with  a  cyanogen  odor. 


COPPER    AMMONIUM    SULPHATE. 

(NH3)4CuS04. 

COPPER    POTASSIUM    SULPHATE. 

CuK3(SO)3  +  6H3O. 

Ammonium  double-salt. — 30  grams  blue  vitriol  are 
dissolved  in  100  c.  c.  ammonia-solution  of  0,962  sp.  gr. 
150  c.  c.  alcohol  are  then  placed  into  a  high,  narrow  cy- 
linder, and  by  means  of  a  long-stemmed  dropping  funnel 
20  c.  c.  water  are  carefully  poured  into  the  alcohol ;  then 
the  copper  solution  is  added  in  a  very  fine  stream,  so  that 
it  will  gather  at  the  bottom  of  the  cylinder,  and  is 
separated  from  the  alcohol  by  the  water.  Upon  standing 
from  i  to  4  weeks  it  forms  large  dark  blue  crystals. 

Potassium  double-salt. — 100  grams  blue  vitriol  in  a 
saturated  solution  at  70°  C.  are  mixed  with  a  solution  of 
69,8  grams  potassium  sulphate  and  7  c.  c.  cone,  sulphuric 
acid.  On  cooling  the  whitish-blue  crystals  of  the  double- 
salt  separate. 

Determine  the  copper  value  of  the  salts :   Of  the  am- 


/6  LABORATORY    MANUAL    OF 

monia  double-salt  by  simply  annealing  and  weighing  the 
remaining  copper  oxide;  of  the  potassium  double-salt  by 
precipitating  with  a  piece  of  cadmium  or  zinc  in  a  weighed 
platinum  dish  from  the  diluted  solution  made  faintly  acid 
with  hydrochloric  acid.  When  a  sample  of  the  discolored 
solution  no  longer  reacts  with  sulphureted  hydrogen  water, 
rinse  with  a  little  hydrochloric  acid,  then  with  hot  water, 
and  lastly  with  alcohol;  dry  at  100°  C.  and  weigh. 


CUPRIC    SULPHATE. 
CuSO4,5H2O. 

This  reagent  may  be  obtained  in  a  state  of  great  purity 
from  the  residue  remaining  in  the  flask  in  the  process  of 
preparing  hydrogen  sodium  sulphite  by  treating  with 
water,  applying  heat,  filtering,  adding  a  few  drops  of  nitric 
acid,  boiling  for  some  time,  allowing  to  crystalize,  rnd 
purifying  the  salt  by  recrystallization. 

After  precipitation  by  hydrogen  sulphide,  ammonia 
and  ammonium  sulphide  must  leave  the  filtrate  unaltered. 


CUPROUS    OXIDE. 

CuoO. 

A  fairly  concentrated  solution  of  copper  sulphate  along 
with  excess  of  sodium  chloride  is  thoroughly  reduced  by 
treatment  with  gaseous  sulphurous  anhydride  ;  the  excess 
of  the  latter  is  then  expelled  by  heating,  and  solid  sodium 
carbonate  is  added  to  the  hot  solution ;  bright  red  cuprous 
oxide  is  precipitated,  and  is  readily  washed  by  decantation.* 


E.  J.  RUSSELL,  Chem.  News,  68,  308. 


INORGANIC    PREPARATIONS*^;  77 


CUPROUS    AMMONIUM     IODIDE. 
4NH3Cu3I4. 

IOO  grams  of  an  ammoniacal  solution  of  cupric  oxide 
containing  7  to  8  per  cent  is  mixed  with  an  equal  weight 
of  a  10  per  cent  solution  of  iodine  in  alcohol.  A  brown 
precipitate  of  nitrogen  iodide  is  formed,  but  this  readily 
disappears  on  warming,  and  if  the  liquid  is  heated  for  about 
an  hour  on  the  water  bath  it  becomes  green  and  deposits 
brilliant  green  needles,  which  must  be  dried  as  quickly  as 
possible.  They  have  the  composition  4NH3,Cu3l4  or 
4NH3Cu3I2,CuI2  and  alter  rapidly  when  exposed  to  air, 
losing  ammonia  and  iodine,  and  eventually  changing  to 
cuprous  iodide.  The  crystals  are  insoluble  in  water,  but 
are  decomposed  by  prolonged  boiling.  They  are  only  de- 
composed by  potash  after  prolonged  boiling,  but  they 
dissolve  readily  in  ammonia,  and  the  solution  yields  cu- 
prammonium  iodide  when  evaporated.  If  the  green  solu- 
tion obtained  as  above  is  boiled  with  metallic  copper  until 
it  becomes  colorless  and  is  then  allowed  to  cool,  it  deposits 
cuprosoammonium  iodide  in  brilliant  white  needles  5  to  6 
mm.  long.  If  the  mixture  of  ammoniacal  copper  solution 
and  alcoholic  iodine  is  allowed  to  stand  with  exposure  to 
air  at  the  ordinary  temperature,  the  nitrogen  iodide  slowly 
dissolves,  and  after  some  hours  the  liquid  deposits  cupram- 
monium  iodide  in  octahedral  crystals.  If  the  ammoniacal 
solution  is  boiled  with  iodine  for  several  hours  without  ad- 
dition of  alcohol,  and  is  then  cooled,  it  deposits  cupram- 
monium  iodide  in  tetrahedral  crystals. 


78  LABORATORY    MANUAL   OF 


CUPROAMMONIUM     TETRA  IODIDE. 
4NH3CuI2,I2. 

Is  obtained  in  brilliant  black  crystals,  green  by  trans- 
mitted light,  by  boiling  100  c.  c.  of  the  amnioniacal  copper 
solution  with  20  grams  of  iodine,  and  allowing  the  liquid 
to  cool.  If  a  further  quantity  of  20  grams  of  iodine  is  dis- 
solved in  the  mother  liquid  from  these  crystals,  the  liquid  on 
cooling  deposits  cuproammonium  hexiodide  4NH3,CuI2l4, 
in  rectangular  tablets,  which  are  brown  by  transmitted 
light.  This  compound  is  usually  obtained  by  mixing  a 
warm  solution  of  cuproammonium  nitrate  with  a  solution 
of  iodine  in  potassium  iodide. 


CUPROUS    PHOSPHIDE. 
CugPg. 

When  red  phosphorous  is  immersed  in  an  ammoniacal 
solution  of  copper  sulphate,  it  becomes  coated,  as  is  well 
known,  with  a  greyish  deposit,  which  is  a  mixture  of 
cuprous  phosphide  and  metallic  copper ;  the  same  occurs 
with  an  amnioniacal  solution  of  copper  phosphate,  but  the 
transformation  is  never  complete,  even  at  100°  C.  If, 
however,  red  phosphorous  is  heated  with  a  large  excess  of 
copper  phosphite  and  water  in  a  sealed  tube  for  four  hours 
at  130°  C.,  its  entire  conversion  is  effected.  The  product 
is  washed  quickly  with  aqueous  ammonia  and  water  in 
succession,  and  dried  in  a  vacuum.  If  the  temperature  hac 
not  exceeded  that  specified,  it  is  not  contaminated  with 
metallic  copper.* 

*  By  A.  GRANGER,  Compt.  rend.,  117,  231-232. 


INORGANIC    PREPARATIONS.  79 

Cuprous  phosphide,  Cu2,Pg,  is  a  grey  powder  resembling 
plumbago  in  appearance.  It  is  attacked  by  chlorine  and 
bromine  in  the  cold,  and  is  readily  dissolved  by  dilute 
acetic  acid ;  a  mixture  of  it  with  potassium  nitrate  or 
chlorate  detonates  violently  when  struck.  When  heated 
in  contact  with  air,  it  is  oxydized  to  copper  phosphate.  It 
is  decomposed  by  heat  into  products  identical  with  those 
yielded  by  cupric  phosphide.  It  is  slightly  soluble  in 
hydrochloric  acid,  yielding  a  solution  from  which  cuprous 
oxide  is  precipitated  by  potash,  and  which,  when  super- 
saturated with  ammonia,  precipitates  metallic  silver  from 
ai\  ammoniacal  solution  of  silver  nitrate. 


PURE     SILVER.       . 

Ag. 

a.  Crystallized    Silver. — Any     weighed    quantity    of 
technical    silver    (coin    or    broken    plate)    is  dissolved   in 
nitric     acid,     filtered     and     dried.      The    dried    mass     is 
fused  until   it  begins   to  turn    black,   dissolved    in   water, 
filtered    and    diluted    to    such    a    degree    that    the    solu- 
tion   contains    2     per    cent,    silver.        It    is    now    made 
strongly   ammoniacal  in   the  cold  and  sodium    bisulphite 
solution  added  until   a  sample   of  the  blue  solution  is  de- 
colorized   on    boiling.       The    greater   part    of    the    silver 
separates  in  crystals   as   the  solution  cools,  the  remainder 
by   warming  at  6oQ  to  /0s  C.     The  silver  is  washed  with 
water,  then  digested  several  times  with  concentrated  am- 
monia,  again  washed  with   water,  dried  on  the  waterbath 
and  weighed. 

b.  Molecular   Silver  from    Residues. — Silver  residues 
together  with  zinc  sticks   are  boiled  with  addition  of  hy- 


80  LABORATORY    MANUAL    OF 

drochloric  acid.  The  reduced  silver,  freed  mechanically 
from  the  undissolved  zinc,  is  washed  well  by  decantation, 
then  dissolved  in  nitric  acid  and  precipitated  with  hydro- 
chloric acid.  The  decanted  and  washed  silver  chloride  is 
placed,  while  still  moist,  in  soda  lye,  kept  boiling  in  a  porce- 
lain dish  and  adding  at  intervals  a  few  c.  c.  of  cone,  grape 
sugar  solution,  until  a  filtered  and  washed  sample  of  the 
gray  silver  powder  dissolves  completely  in  nitric  acid. 
Wash,  dry  and  weigh  as  described  in  a. 

The  black  color  appearing  in  fusing  the  impure  nitrate 
arises  from  the  decomposition  of  the  copper  nitrate; 
to  avoid  any  loss  of  silver  it  is  not  heated  until  all  the 
copper  salt  has  been  converted  into  oxide  ;  but  the  separa- 
tion of  silver  from  the  copper  is  so  managed  that  the  silver 
from  the  ammoniacal  solution  is  precipitated  in  metallic 
form  by  sulphurous  acid,  while  the  copper,  under  these 
circumstances,  is  reduced  to  protoxide,  which  remains  dis- 
solved in  the  ammoniacal  solution. 

Dissolve  a  sample  of  the  silver  in  nitric  acid  free  from 
chloride,  and  note  any  sediment  (gold,  silver,  chloride,  tin 
dioxide) ;  precipitate  the  solution  with  hydrochloric  acid 
and  test  the  filtrate  for  heavy  metals. 


PREPARATION  OF  PURE  COLLOIDAL  SILVER. 

Solutions  of  ferrous  sulphate  (150  grams  of  the  salt  in 
500  c.  c.  of  the  solution)  and  of  sodium  citrate  (280  grams 
of  the  salt  in  700  c.  c.  of  the  solution)  are  mixed  and 
poured  into  a  10  per  cent,  solution  of  silver  nitrate  (500 


INORGANIC    PREPARATIONS.  8  I 

c.  c.).  Day-light  need  not  be  excluded,  but  it  is  ad- 
visable to  divide  the  mixture  into  five  equal  portions,  as 
small  quantities  can  be  dealt  with  more  easily  than  large. 
At  the  end  of  half  an  hour  the  supernatant  liquid  is  re- 
moved from  the  precipitated  colloidal  silver  with  a  pipette, 
and  the  silver  is  thrown  on  to  a  filter  (Schleicher  and 
SchuH's  No.  590  paper),  filtered  under  diminished  pressure, 
and  dissolved  on  the  filter  in  the  minimum  quantity  of 
water ;  solutions  may  thus  be  obtained  containing  20 
grams  of  silver  per  litre.  To  this  solution  absolute  alcohol 
is  added  with  agitation  until  coagulation  is  perceptible, 
and,  after  remaining  for  several  days,  the  colloid  is  fil- 
tered under  a  diminished  pressure  of  10  to  20  mm.  on  a 
Pasteur  filter-tube,  when  it  forms  a  beautiful  iridescent 
incrustation.  Colloidal  silver  in  this  state  of  purity  is 
soluble  in  alcohol,  and  cannot  therefore  be  washed  with 
this  liquid  to  remove  the  last  traces  of  crystalloids.  By 
this  method  a  product  containing  only  .03  to  .05  percent,  of 
iron  is  obtained.* 


SILVER    POTASSIUM     CARBONATE. 

AgKCO3. 

150  grams  of  potassium  carbonate  are  dissolved  in  150 
c.  c.  of  water,  cooled  and  agitated  with  1 5  grams  of  potas- 
sium hydrogen  carbonate.  When  the  liquid  is  saturated 
with  the  latter  salt  at  ordinary  temperature,  it  is  filtered 
and  mixed  with  a  solution  of  one  gram  of  silver  nitrate  in 
25  c.  c.  of  water.  In  order  to  obtain  large  crystals,  the  liquid 
containing  the  precipitate  is  heated  with  continual  agita- 

*  By  E.  A  SCHNEIDER,  Ber.  25,  1281-1284. 
0 


82  LABORATORY    MANUAL    OF 

tion.  The  precipitate  dissolves,  and  when  the  liquid  is 
cooled  it  deposits  long,  transparent  crystals  with  a  brilliant 
lustre:  sp.  gr.  3.769.  They  do  not  blacken  when  exposed 
to  light  except  in  the  presence  of  organic  matter,  and  when 
treated  with  water  the  silver  carbonate  which  remains  re- 
tains the  form  of  the  original  crystals.  When  heated  the 
compound  loses  carbonic  anhydride,  and  at  a  higher  tem- 
perature the  silver  oxide  which  is  formed  gives  off  oxygen. 
The  crystals  are  microscopic,  rectangular  lamellae  with 
a  terminal  angle  closely  approaching  90°.  The  refraction 
is  almost  identical  with  that  of  apatite.* 


PURE     GOLD. 

Au. 

Technical  gold  (broken  pieces  of  jewelry,  a  coin  or  crude 
washgold)  is  broken  into  pieces  as  small  as  possible,  weighed, 
placed  in  a  small  flask  and  concentrated  hydrochloric  acid 
poured  over  it.  The  flask  is  heated  in  a  sand-bath,  and 
from  time  to  time  cone,  nitric  acid  dropped  into  it.  After 
all  is  dissolved  evaporate  in  a  porcelain  dish  on  the  water- 
bath,  carefully  avoiding  all  dust,  until  the  remaining  dark- 
red  solution  solidifies  on  cooling.  Then  dissolve  in  plenty 
of  water,  filter  from  the  separated  silver  chloride  and  pre- 
cipitate the  filtrate  hot  with  ferrous  chloride  solution  in 
excess.  The  separated  gold  in  powder  is  decanted,  boiled 
several  times  with  diluted  hydrochloric  acid,  gathered  on 
an  ashless  filter,  fused  in  a  porcelain  crucible  and  weighed. 
In  case  larger  quantities  of  gold  are  refined,  a  little  platinum 


*  A  DE  SCHULTEN,  Compt.  Rend.  105,  811. 


INORGANIC    PREPARATIONS.  8$ 

and  palladium  (even   thallium)  can  be  separated  from  the 
filtrate  with  iron  or  zinc. 

The  gold  obtained  in  form  of  a  reddish  powder  should 
not  impart  a  trace  of  yellowish  color  (iron)  to  boiling  hy- 
drochloric acid.  If  a  weighed  quantity  is  once  more 
subjected  to  the  refining  process  described  above  the 
weight  should  remain  constant. 


AURIC    CHLORIDE,    OR    GOLD    TRICHLORIDE. 

AuCl3. 

Take  fine  shreds  of  gold,  which  may  be  alloyed  with 
silver  or  copper,  treat  them  in  a  flask  with  nitrohydrochloric 
acid  in  excess,  and  apply  a  gentle  heat  until  no  more  of 
the  metal  dissolves,  then  dilute  the  solution  with  10  parts 
of  water.  If  the  gold  was  alloyed  with  copper — which  is 
known  by  the  brownish-red  precipitate  produced  by  po- 
tassium ferrocyanide  in  a  portion  of  the  solution  diluted 
with  water — mix  it  with  solution  of  ferrous  sulphate  in 
excess.  This  will  reduce  the  auric  chloride  to  metallic 
gold,  which  will  separate  in  the  form  of  a  fine  brownish- 
black  powder ;  wash  the  powder  in  a  small  flask,  and  dis- 
solve it  in  nitrohydrochloric  acid  ;  evaporate  the  solution 
on  the  waterbath,  and  dissolve  the  residue  in  30  parts  of 
water.  If  the  gold  was  alloyed  with  silver,  the  latter 
metal  remains  as  chloride,  upon  treating  the  alloy  with 
nitrohydrochloric  acid.  In  that  case  evaporate  the  solu- 
tion at  once,  and  dissolve  the  residue  in  water  for  use. 


84  LABORATORY    MANUAL    OF 


AUROSO-  AURIC     CHLORIDE. 


By  leading  a  stream  of  dry  chlorine  for  30  minutes 
over  gold,  precipitated  from  a  solution  of  gold  chloride  by 
sulphurous  acid,  50  to  70  grams  of  gold  may  be  converted 
into  a  homogeneous  mass  corresponding  with  the  formula 
Au2Cl4.  The  reaction  is  started  by  gentle  heating,  but  the 
necessary  temperature  is  then  maintained  by  the  heat 
evolved  in  the  reaction,  provided  that  cooling  is  prevented 
by  surrounding  the  tube  with  cotton  or  glass  wool.* 


ANHYDROUS    MAGNESIUM    CHLORIDE. 
MgCI2. 

500  grams  crytallized  magnesium  chloride  and  500 
grams  sal  ammoniac  are  dissolved  in  a  very  small  quantity 
of  water,  filtered  in  a  porcelain  dish  and  dried  in  a  silver 
dish.  The  solid  mass  is  broken  while  hot  and  dried  in 
small  portions  on  porcelain  or,  better,  on  platinum  dishes 
(the  mixture  corrodes  base  metals,  silver  also,  at  a  higher 
temperature).  The  operation  occupies  some  time  and  is 
to  be  carried  out  with  great  care,  as  even  very  small 
quantities  of  water  frustrate  the  success  of  the  experi- 
ment. Dry  in  portions  on  several  gas  stoves  and  regulate 
the  heat  so  that  an  escape  of  ammonium  chloride  vapor  does 
not  take  place.  Powder  the  portions  from  time  to  time  in 
a  hot  mortar,  continue  drying  until  the  product,  on  heat- 


J.  THOMSEN,  J.  pr.  Chem.  [2]  37,  105. 


INORGANIC    PREPARATIONS.  85 

ing,  no  longer  cakes  and  only  consider  the  operation 
completed  when  a  sample  heated  in  a  test  tube  shows  no 
moisture ;  after  driving  off  the  ammonium  chloride  there 
remains  a  clear  solution,  forming  radiant  crystals  upon 
cooling.  Then  pour  the  powder*  while  still  hot  in  a 
spacious  platinum  crucible,  close  with  a  well-fitting  cover 
and  place  into  the  Roessler  furnace  which  has  previously 
been  heated.  After  the  ammonium  chloride  is  driven  out, 
again  fill  the  crucible  t  with  the  loose  powder,  and  con- 
tinue heating  until  the  entire  mass  is  fused.  The  solidified 
magnesium  chloride,  which  is  easily  removed  from  the 
crucible,  should  be  placed  in  a  well-stoppered  bottle  while 
still  warm. 

Crystallized  magnesium  chloride  can  be  rendered  an- 
hydrous and  the  formation  of  a  basic  salt  prevented  by 
heating  it  in  a  current  of  hydrogen  chloride.| 

Crystallized  magnesium  chloride  on  heating  loses  the 
largest  quantity  of  its  chlorine  in  the  form  of  hydrochloric 
acid;  on  the  other  hand,  the  double-salt  (NHJgMgC^ 
can,  by  heating  carefully,  be  volatilized  without  decompo- 
sition. On  igniting  this  double-salt  anhydrous  magnesium 
chloride  remains. 

(NH4)3MgCl4  =  MgCl2  +  2NH4C1. 

Magnesium  chloride  crystallizes  in  large  radiant  g^ssy 
crystals,  not  unlike  fused  sodium  acetate,  which  melt  readily 
on  heating  and  volatilize  at  red-heat.  The  vapors  decom- 


*  If  the  dried  substance  is  to  be  preserved,  this  must  be  done  in  well- 
stoppered  vessels.  Before  using  the  mass  it  should  be  dried  for  a  short  time 
on  the  gas  stove. 

f  When  in  a  red-hot  condition  the  crucible   musi   not   be  opened  on 
account  of  the  volatility  of  the  magnesium  chloride. 
\  W.  HEMPEL,  Ber.  21,  897. 


86  LABORATORY    MANUAL   OF 

pose  aqueous  vapor  instantly,  forming  hydrogen  chloride. 
The  very  hydroscopic  salt  should  form  a  clear  solution  in 
warm  water. 


CRYSTALLIZED    NORMAL    MAGNESIUM    CAR- 
BONATE. 
MgCO3  +  3  H2O. 

If  freshly  precipitated  magnesium  carbonate,  made  by 
mixing  equivalent  amounts  of  magnesium  sulphate  and  so- 
dium carbonate,is  shaken  with  a  solution  of  potassium  hydro- 
gen carbonate  at  the  ordinary  temperature,  much  of  the  mag- 
nesium carbonate  dissolves,  crystallizes  out  of  the  filtered 
solution  after  a  time ;  the  separation  is  ended  in  24  hours. 
The  same  occurs  if  sodium  hydrogen  carbonate  is  used ;  it 
dissolves  relatively  more  .of  the  magnesium  carbonate,  but 
the  crystals  obtained  are  smaller.  Solutions  containing 
respectively  67.5  grams  of  potassium  and  12.96  grams  of 
sodium  hydrogen  carbonate  per  liter  dissolved,  respectively, 
18.73  and  9.95  grams  of  magnesium  carbonate.  The  crys- 
tals have  the  composition  4MgCo3  -f  15H3O  ;  after  four 
weeks  in  dry  air,  or  15  hours  in  a  vacuum  dessicator 
over  sulphuric  acid,  they  have  the  composition  2MgCO3  -f 
6H3O;  after  heating  at  170°  C.  the  composition  MgCO3 + 
l/3  —  VeHgO.  The  reaction  is  that  a  double  sesquicarbonate 
of  magnesium  and  the  alkali  metal  is  formed,  and  that  this 
afterwards  decomposes,  magnesium  carbonate  being  pre- 
cipitated, and  carbonic  anhydride  liberated,  which  latter 
regenerates  the  alkali  bicarbonate  with  the  alkali  sesqui- 
carbonate now  present. 

Alkali  bicarbonates  do  not   dissolve  calcium  carbonate 


INORGANIC    PREPARATIONS.  8/ 

or  ferric  hydroxide,  and  upon  this  fact  a  technical  process 
for  the  preparation  of  pure  magnesium  carbonate  from 
dolomite,  magnesite,  bitterspar  and  from  kanite  or  caen- 
allite  liquors  has  been  based.  The  mineral  is  powdered, 
dissolved  in  commercial  hydrychloric  acid  and  the  iron 
oxydized  by  warming  gently  with  a  little  nitric  acid.  The 
solution  is  then  precipitated  with  sodium  carbonate  in  slight 
excess,  the  filtered  precipitate  shaken  with  a  sufficiently 
strong  solution  of  alkali  bicarbonate,  and  the  solution  fil- 
tered after  a  lapse  of  20  minutes  and  set  aside  to  crystal- 
lize. The  mother  liquor  can  be  used  repeatedly  for  the 
extraction.* 


MAGNESIUM    BASIC     CARBONATE. 

Mg(OH)2,MgC03. 

Prepare  a  strong  solution  of  magnesium  sulphate  in 
water,  kieserite  serves  very  well ;  to  the  cold  filtered  solu- 
tion add  sodium  carbonate  solution  in  slight  excess,  mix 
well  in  the  cold,  filter  and  wash  slightly ;  the  filtrate  may 
be  used  to  prepare  glauber-salt ;  transfer  the  precipitate 
of  magnesium  carbonate  to  a  suitable  vessel,  add  water  and 
boil  for  15  minutes;  filter  and  wash  on  a  filtering  plate, 
suck  as  dry  as  possible,  remove  from  filter  and  dry  at 

o    /^* 

100    C. 

POROUS     CALCIUM     CHLORIDE. 

CaCl2. 

One  litre  of  the  solution  remaining  from  the  evolution 
of  carbonic  acid  from  marble  and  hydrochloric  acid  (crude) 


*  K.  KIPPENBERGER,  Zeit.  anor.  Chem.  6,  177. 


88  LABORATORY    MANUAL    OF 

and  which  no  longer  reacts  with  marble  is  warmed  and 
then  precipitated  with  milk  of  lime,  made  from  35  grams 
caustic  lime,  in  an  iron  pot  of  2  litres  capacity  and  filtered.* 
After  the  strongly  alkaline  solution  has  been  boiled,  mix 
the  filtrate  with  hydrochloric  acid  to  a  strong  acid  reaction 
and  evaporate  it  on  the  gas  stove,  with  further  addition  of 
acid,  in-,  a  porcelain  dish  of  j£  litre  capacity.  As  soon  as 
a  coating  of  salt  begins  to  form  the  heat  is  reduced,  a  little 
fuming  hydrochloric  acid  is  added,  and  the  whole  left  stand- 
ing quietly  without  stirring;  the  mass  becomes  entirely  dry 
in  the  course  of  from  four  to  five  hours.  Now  carefully  re- 
move the  calcium  chloride  from  the  dish  with  a  knife, 
break  the  large  pieces  while  still  hot  in  a  warm  mortar, 
screen  the  pieces  as  quickly  as  possible  in  sieves  from  I  to  5 
mm  mesh,  and  fill  immediately  into  well-stopperd  speci- 
men bottles. 

The  caustic  lime  precipitates  from  the  marble  solution 
magnesia,  as  well  as  the  oxides  of  iron  and  manganese. 
(Very  often  in  standing,  basic  cakium  chloride  3CaO, 
CaClfc  +  15H2O  separates  from  the  filtrate  in  long  prisms). 
In  evaporating  to  dryness  the  solution  must  be  acidified 
with  hydrochloric  acid  and  the  heating  must  be  a  gradual 
one,  otherwise  the  calcium  chloride  will  lose  HC1.  and 
take  on  a  strong  alkaline  reaction. 

Porous  calcium  chloride  is  a  pure  white,  porous,  very 
hydroscopic  mass,  which  dissolves  clearly  in  water,  and  in 
alcohol  the  water  solution  should  show  a  reaction  which  is 
slightly  alkaline. 


*  In  place  of  this  you  can  also  proceed  from  the  residue  of  ammonia 
production,  consisting  of  a  mixture  of  calcium  chloride  and  surplus  lime. 
Boil  the  same  with  water  until  the  last  traces  of  ammonia  have  passed  away, 
then  filter  and  continue  as  stated  above. 


INORGANIC    PREPARATIONS.  89 


CALCIUM     CHLORIDE. 
CaCl2,  crystallized  +6H2O. 

Dilute  I  part  of  crude  hydrochloric  acid  with  6  parts  ot 
water,  and  add  thereto  marble  or  chalk  until  the  last  por- 
tion added  remains  undissolved ;  add  now  some  slacked 
lime,  then  hydrogen  sulphide,  until  a  filtered  portion  of  the 
mixture  is  no  longer  altered  by  ammonium  sulphide. 
Then  let  the  mixture  stand  covered  for  12  hours  at  a 
gentle  heat,  filter,  exactly  neutralize  the  filtrate,  concen- 
trate by  evaporation  and  crystallize. 

Solution  of  pure  calcium  chloride  must  be  perfectly 
neutral,  and  neither  be  colored  or  precipitated  by  ammo- 
nium sulphide ;  nor  ought  it  to  evolve  ammonia  when 
mixed  with  potassa  or  lime. 


CALCIUM     CARBONATE. 

CaCo3. 

Solution  of  pure  calcium  chloride  is  heated  to  boiling 
and  precipitated  by  a  slight  excess  of  solution  of  ammo- 
nium carbonate  with  addition  of  some  ammonia.  The 
precipitate  is  washed  five  or  six  times  with  hot  water  by 
decantation,  then  is  brought  upon  a  filter  and  further  edul- 
corated until  the  washings  give  no  turbidity  with  silver 
nitrate.  The  contents  of  the  filter  are  then  dried  and 
bottled. 

Calcium  carbonate  for  use  as  a  flux  must  be  free  from 
salts  of  the  fixed  alkalies.  When  washed  with  hot  water 
the  washing  must  yield  no  residue  when  evaporated  to 
dryness. 


90  LABORATORY  MANUAL  OF 

CRYSTALLINE     MONOCALCIUM     PHOSPHATE. 

CaH4(P04),. 

Neither  the  crystalline  nor  the  honey-like  commercial 
variety  of  monocalcium  phosphate  corresponds  with  the  for- 
mula CaH4(PO4)2,  owing  to  the  free  sulphuric  acid  in 
the  crude  liquor  acting  on  the  phosphate  during  evapora- 
tion. By  leaving  tricalcium  phosphate  in  contact  with  a 
solution  of  the  honey-like  commercial  variety  for  some 
time,  a  solution  is  obtained  which,  on  gentle  evaporation, 
yields  crystals  of  pure  monocalcium  phosphate.* 


CALCIUM    CHROMATE. 

CaCr2O4. 

The  process  is  based  on  the  fact  that  when  chromium 
oxide  (CrgOs)  is  heated  with  a  mixture  of  calcium  chloride 
and  oxide,  a  chromite  is  formed  (CaCr2O4)  which  absorbs 
oxygen  from  the  air  and  yields  calcium  chromate.  The 
finely  powdered  mineral  is  mixed  with  paste  composed  of 
lime,  calcium  carbonate  and  a  concentrated  solution  of 
calcium  chloride,  in  such  proportion  that  the  lime  and 
the  calcium  carbonate  are  slightly  in  excess,  of  the  amount 
necessary  to  combine  with  the  chromium  oxide  present, 
while  the  calcium  chloride  is  about  one-third  of  the  total 
lime  used.  The  mixture,  on  exposure  to  air,  hardens  and 
is  moulded  into  bricks,  which  are  dried  and  subsequently 
roasted  at  a  temperature  sufficient  to  convert  the  calcium 
carbonate  into  lime.  The  bricks  are  exposed  to  the  action 
of  air  for  about  one  month,  then  lixiviated  with  hot  water 
to  remove  the  calcium  chloride,  and  the  residue  containing 

*  G.  POINTET,  Bull.  Soc.  Chim.  [3]  5,  254. 


INORGANIC   PREPARATIONS.  91 

the  calcium  chromate  is  treated  with  alkali  carbonate  or 

sulphuric  acid   in   the   usual  way,  according  as   an   alkali 
chromate  or  chromic  acid  is  required.* 


ZINC    FREE    FROM    ARSENIC. 

Zn. 

One  kilo  commercial  zinc  is  melted  in  a  hessian  cru- 
cible. Into  the  red-hot  metal  plunge  pieces  of  anhydrous 
magnesium  chloride,  forcing  them  to  the  bottom  of  the 
crucible,  and  allow  them  to  remain  there  until  dissolved. 
To  retain  the  specifically  light  chloride  below  the  fused 
metal  an  iron  wire  is  employed,  the  lower  part  of  which 
is  twisted  into  a  close  spiral.  Fasten  in  the  small  bell  so 
constructed,  the  magnesium  chloride  by  means  of  a  little 
flower-wire,  and  press  the  wire  into  the  metal.  After 
adding  1 5  grams  of  the  chloride  allow  the  crucible  to  cool 
sufficiently  to  prevent  the  metal  from  igniting  upon  open- 
ing it,  and  (the  metal  should  be  still  liquid)  pour  it  in 
the  finest  possible  stream  into  a  pail  of  water.  The  gran- 
ules upon  removal  from  the  water  are  drained  and  dried 

by  heat. 

3MgCl2  +  2As  =  3Mg  +  2AsCl3. 

The  arsenic  chloride  and  undecomposed  magnesium  chlo- 
ride pass  off  in  thick  clouds. 

The  zinc  so  obtained  contains  magnesium  and,  so  dif- 
ferently from  c.  p.  zinc,  dissolves  very  readily  in  diluted 
acids.  To  test  it  for  arsenic,  pour  over  it,  in  a  test  tube, 
dilute  (i.i)  hydrochloric  acid  and  cover  the  tube  with  a 
small  filter,  the  tip  of  which  is  moistened  with  a  drop  of 


J.  MASSIGNON  and  E.  VATSL,  Bull.  Soc.  Chim.  [3]  5,  371. 


92  LABORATORY    MANUAL   OF 

cone,  silver  solution  (i.i).  Yellow  silver  arsenite  Ag3AsO3 
forms  after  a  time,  which  turns  black  and  decomposes  in 
water.  * 


ZINC     EISEN. 

From  one  10  two  pounds  of  zinc  are  melted  in  a  clay 
crucible,  3  to  3.5  ozs.  of  anhydrous  sodium  ferrous  chloride 
are  thrown  in,  and  the  crucible  is  immediately  covered  ; 
violent  reaction  ensues,  and  the  alloy  is  produced ;  it  is 
very  brittle,  has  a  full  metallic  lustre,  and  is  easily  pul- 
verized.t 


STRONTIUM     HYDROXIDE. 

Sr(OH)2  +  8H20. 

A  well  mixed  mass  of  150  grams  finely  powdered 
celestine  and  50  grams  wood  charcoal  is  pressed  into  a 
hessian  crucible  and  covered  with  a  layer  of  powdered 
coal.  Close  the  crucible  with  an  accurately  fitting  iron 
cover,  provided  with  a  rim,  and  heat  at  white  heat  for  an 
hour  in  the  Roessler  gas  furnace.  The  cool  product  should 
dissolve  in  dilute  hydrochloric  acid  with  vigorous  evolution 
of  sulphureted  hydrogen,  leaving  only  a  slight  coaly 
residue ;  test  a  portion  in  this  manner  :  Suspend  the  mass 
in  a  porcelain  dish  in  a  litre  of  hot  water,  and  add  to  the 
solution  scales  of  copper  (100  to  150  grams  which  have  been 
moistened  with  a  little  HNO3  and  then  annealed),  until  a 
filtered  sample  treated  with  lead  acetate  no  longer  pro- 


*  L.  L'HoTE,  Compound  98,  1491. 

f  H.  N.  WARREN,  Chem.  News,  55,  100. 


INORGANIC    PREPARATIONS.  93 

duces  a  brownish-black  precipitate.  Then  filter  hot  into  a 
beaker,  boil  the  residue  with  100  c.  c.  water,  cover  the 
entire  filtrate,  and  allow  it  to  crystallize.  After  the  lapse 
of  24  hours  the  liquid  is  poured  off  from  the  crystals, 
which  are  very  quickly  dried  on  an  earthen  plate  and 
placed  in  a  closed  and  paraffined  vessel.  The  solution  is 
rapidly  evaporated  to  300  c.  c  in  an  iron  dish,  to  obtain  a 
second  crop  of  crystals. 

The  strontium  sulphate,  by  ignition  with  charcoal  and 
exclusion  of  air,  is  transformed  into  strontium  sulphide, 
which  by  the  action  of  copper  oxide  is  converted  into  stron- 
tium hydroxide:  SrSo4  +  4C  =  SrS  +  4CO  ;  SrS  +  CuO  + 
H^O  =  Sr(OH2)  4-  CuS. 

Strontium  hydroxide  crystallizes  in  perfectly  clear, 
easily  efflorescent  square  tablets  or  needles  of  strong 
alkaline  taste,  dissolving  readily  and  without  residue  in 
hot  water.  It  melts  easily  on  warming,  and  on  further 
heating  solidifies  again  to  a  white  mass  with  loss  of  its  eight 
molecules  of  water  of  crystallization ;  at  higher  tempera- 
tures it  melts  once  more,  and  finally  passes  into  strontium 
oxide.  An  acetic  acid  solution  should  not  be  precipitated 
by  potassium  dichromate  (Bar.ium),  but  should,  on  the 
other  hand,  be  precipitated  so  completely  by  HgSC^  that 
ammonium  oxalate  does  not  form  a  precipitate  in  the 
filtrate  (absence  of  lime). 


PREPARATION    OF    PURE    STRONTIUM   SALTS. 

The  following    process   is   given   for  obtaining  a  pure 

strontium   salt    from  a  barytostrontianite  containing   iron, 

aluminium,  magnesium,  calcium  and  barium  as  impurities: 


94  LABORATORY    MANUAL    OF 

The  mineral  or  the  sulphide  resulting  from  the  reduction 
of  the  sulphate  is  dissolved  in  such  a  quantity  of  hydro- 
chloric acid  (20  per  cent.)  as  to  leave  a  little  undissolved. 
The  aluminum  and  iron  are  precipitated  by  ammonia,  fil- 
tered off,  and  excess  of  sulphuric  acid  added.  The  pre- 
cipitate is  washed  first  with  dilute  sulphuric  acid  (i  to  2  per 
cent.)  and  finally  with  water;  it  is  thus  freed  from  magne- 
sium and  calcium.  It  is  now  digested  in  the  cold  for 
some  days  with  ammonium  or  potassium  carbonate  solu- 
tion (10  per  cent.),  washed  well,  the  residue  treated  with 
dilute  hydrochloric  acid,  and  the  solution  decanted  ; 
after  remaining  for  24  hours  this  is  filtered,  and  200  grams 
of  hydrochloric  acid  (sp.  gr.  1.17)  per  litre  are  added 
to  it,  together  with  2  or  3  grams  of  precipitated  strontium 
sulphate,  which  may  contain  barium.  After  some  hours 
the  solution  is  filtered,  evaporated  to  dryness,  dissolved  in 
water,  filtered  and  crystallized.  The  spectrum  given  by 
the  salt  thus  obtained  shows  strontium  to  be  the  only  metal 
present.* 

CADMIUM     CARBONATE. 

CdC03. 

IOO  grams  of  cut  or  granulated  commercial  cadmium 
are  placed  in  a  flask  with  400  c.  c.  cold  nitric  acid  of  1.20 
sp.  gr.  Run  the  nitrogen  dioxide  evolved  into  the  drain; 
after  the  action  has  completely  ceased,  pour  the  liquid 
from  the  undissolved  residue  into  a  porcelain  dish  of  6 
litres  capacity ;  dilute  with  4  litres  hot  water  and  add  a 
little  powdered  commercial  ammonium  carbonate,  until  a 


By  BARTHE  and  FALIERES,  Bull.  soc.  Chin.  [3],  7,  104-108. 


INORGANIC    PREPARATIONS.  95 

permanent  precipitate  is  formed  ;  filter  and  precipitate  the 
cadmium  in  the  filtrate  with  about  150  grams  ammonium 
carbonate  ;  decant  several  times  with  hot  water  in  tall  glass 
cylinders,  and  preserve  the  carbonate  as  paste,  or  else  dry 
on  the  water-bath. 

3Cd  +  8HNO3  =3Cd(NO3)2  f  2NO  -f  4H3O. 

The  foreign  metals,  with  the  exception  of  zinc  and  iron,  do 
not  remain  in  solution,  but  are  again  precipitated  in  me- 
tallic form  by  the  surplus  cadmium.  The  iron  precipitates 
with  the  first  portion  of  cadmium  carbonate  : 

3CdCO3  4-  Fe2(NO3)6  +  3H2O  =  3Cd(NO3)2  +  Fe2(OH)6  f 

3CO2. 

The  zinc  is  retained  in  solution  by  the  surplus  ammonium 
salt. 

The  pure  white  salt  passing  into  brown  cadmium  oxide 
on  igniting,  and  easily  dissolving  in  diluted  acids  with  effer- 
vescence, is  to  be  tested  particularly  for  antimony,  bismuth, 
copper,  lead,  iron  and  zinc  according  to  the  usual  method 
of  analysis. 


BARIUM     OXI  DE. 
BaO. 

1 50  grams  of  heavy  spar  are  reduced  with  40  grams 
wood  charcoal,  in  the  same  manner  as  described  for  celes- 
tine  (on  page  92),  and  the  barium  sulphide  obtained  is  de- 
composed in  a  litre,  flask,  with  dropping  funnel  and  gas 
conduit  tube,  by  means  of  dilute  HNO3,  filtered  and 
evaporated  to  crystallization.  Of  this,  or  else  of  commer- 
cial barium  nitrate,  I  y2  kilos  are  gradually  placed  with  an 


96  LABORATORY    MANUAL    OF 

iron  spoon  in  a  red-hot  Hessian  crucible,  which  is  kept  cov- 
ered with  an  earthen  cover.  After  having  added  the  whole 
quantity  the  closed  crucible  is  heated  for  another  hour  at 
very  high  temperature.  After  the  crucible  has  again  partly 
cooled,  remove  the  upper  layer  of  the  barium  manganate, 
the  green-colored  layer  of  the  crucible,  and  fill  the  barium 
oxide  into  small  flasks,  at  once  sealing  them  hermetically. 

The  barium  nitrate  at  first  passes  into  barium  nitrite 
and  then  further  into  barium  oxide,  at  white  heat: 

Ba(NO8)2  =  Ba(NO2)2  +  2O, 
Ba(NO2)2  =  BaO  +  2N  -f  3O. 

Barium  oxide  comes  in  grayish-white  porous  pieces, 
which  evolve  heat  with  water  and  dissolve  completely  in 
dilute  hydrochloric  acid  without  effervescing;  this  solution 
should  not  discolor  permanganate  nor  blue  potassium  iodide 
starch  paper  (barium  nitrate  and  barium  superoxide). 


BARIUM     CHLORIDE. 

BaCl2  +  2H2O. 

a.  From  heavy  spar.  Mix  together  8  parts  of  pul- 
verized barium  sulphate,  2  parts  of  charcoal  powder,  and  I 
part  of  common  rosin.  Put  the  mixture  in  a  crucible  and 
expose  it  in  a  blast  furnace  to  a  long-continued  red  heat. 
Triturate  the  crude  barium  sulphide  obtained,  boil  about  A 
of  the  powder  with  4  times  its  quantity  of  water,  and  add 
hydrochloric  acid  until  all  effervescence  of  hydrogen  sul- 
phide has  ceased,  and  the  fluid  manifests  a  slight  acid  reac- 
tion. Add  now  the  remaining  A  part  of  the  barium  sul- 
phide, boil  some  time  longer,  then  filter,  and  let  the  alkaline 


INORGANIC    PREPARATIONS.  97 

fluid  crystallize.  Drain  the  crystals,  redissolve  them  in 
water,  and  crystallize  again. 

b.  From  witherite.  Pour  10  parts  of  water  upon  i 
part  of  pulverized  witherite,  and  gradually  add  crude  hy- 
drochloric acid  until  the  witherite  is  almost  completely  dis- 
solved. Add  now  a  little  more  finely  pulverized  witherite, 
and  heat,  with  frequent  stirring,  until  the  fluid  has  entirely 
or  very  nearly  lost  its  acid  reaction  ;  add  solution  of  barium 
sulphide  as  long  as  a  precipitate  forms ;  then  filter,  evap- 
orate the  filtrate  to  crystallization,  and  purify  by  crystal- 
lizing again.  For  use,  dissolve  I  part  of  the  barium  chlo- 
ride in  10  parts  of  water. 

Pure  barium  chloride  must  not  alter  vegetable  colors  ; 
its  solution  must  not  be  colored  or  precipated  by  hydrogen 
sulphide,  nor  by  ammonium  sulphide.  Pure  sulphuric 
acid  must  precipitate  every  fixed  particle  from  it,  so  that 
the  fluid  filtered  from  the  precipitate  formed  upon  the  ad- 
dition of  that  reagent  leaves  not  the  slightest  residue  when 
evaporated  on  platinum  foil. 


BARIUM     NITRATE. 
Ba(NO3)2. 

Treat  barium  carbonate,  no  matter  whether  witherite 
or  that  precipitated  by  sodium  carbonate  from  solution  of 
barium  sulphide,  with  dilute  nitric  acid  free  from  chlorides, 
and  proceed  exactly  as  directed  in  the  preparation  of 
barium  chloride  from  witherite. 

Solutions  of  barium  nitrate  must  not  be  made  turbid  by 
silver  nitrate  solutions.  The  other  tests  are  the  same  as 
for  barium  chloride. 


98  LABORATORY    MANUAL    OF 


BARIUM     PEROXIDE. 
Ba02. 

BARIUM     PERHYDRATE. 
Ba(OH)4  +  6H2O. 

A  combustion  tube  is  filled  with  30  grams  powdered  ba- 
rium oxide,  moderately  heated  in  a  combustion  furnace,  and  a 
rapid  current  of  oxygen  dried  with  cone,  sulphuric  acid 
conducted  over  it.  The  solid  peroxide,  after  being  ground 
with  a  little  water,  is  placed  in  50  c.  c.  dil.  hydrochloric  acid 
which  has  been  cooled  to  o°  C.,  then  the  still  faintly  acid 
solution  is  filtered  and  allowed  to  flow  into  500  c.  c.  baryta 
water  which  has  been  cooled  to  o°  C.,  and  saturated  cold. 
The  separated  precipitate,  consisting  of  glistening  crystalline 
scales,  is  sucked  dry,  washed  with  a  little  ice-water,  and 
preserved  as  paste. 

With  moderate  heat  the  barium  oxide  adds  another 
atom  of  oxygen.  The  barium  peroxide  decomposes  with 
hydrochloric  acid:  2BaO3  f-  4HC1  =  2BaCl2  +  2H2O  ;  the 
hydrogen  peroxide  with  baryta:  H3O3  -f  Ba(OH)3  = 
Ba(OH)4. 

The  barium  superoxide  must  not  inflame  by  grinding 
with  water  (property  of  barium  oxide).  The  value  of  the 
perhydrate  is  proven,  if  hydrogen  peroxide  is  produced 
from  the  preparation. 


BARIUM     CARBONATE. 

BaCO3. 

Dissolve  crystallized  barium  chloride  in  water,  heat  to 
boiling,  and  add  a  solution  of  ammonium  carbonate  mixed 


INORGANIC    PREPARATIONS.  99 

with  some  ammonia,  or  of  pure  sodium  carbonate,  as  long 
as  a  precipitate  forms  ;  let  the  precipitate  subside,  decant  five 
or  six  times,  transfer  the  precipitate  to  a  filter,  and  wash 
until  the  wash  water  is  no  longer  made  turbid  by  silver 
nitrate  solution. 

Pure  sulphuric  acid  must  precipitate  every  fixed  particle 
from  a  solution  of  barium  carbonate  in  hydrochloric  acid. 


BARIUM    DITHIONATE. 


DITHIONIC    ACID. 
H3S306+xH20. 

100  grams  finely  powered  black  oxide  manganese  is  elu- 
triated by  mixing  with  water  in  a  large  mortar,  decanted, 
and  the  remaining  coarse  powder  again  mixed  with  water  ; 
this  is  repeated  until  the  entire  mineral  is  suspended  in 
water,  then  allow  it  to  settle  in  tall  cylinders  ;  the  water  is 
removed  by  means  of  a  syphon,  and  the  black  oxide  of  man- 
ganese brought  into  a  liter  flask  with  y2  litre  water.  A 
current  of  sulphur  dioxide  is  passed  through  the  mixture, 
the  flask  being  cooled  with  ice.  When  the  bulk  of  the 
black  oxide  manganese  has  dissolved  add  to  the  solution 
which  has  been  heated  in  a  dish  cone,  barium  hydrate 
solution  until  a  filtered  sample  fails  to  yield  a  flesh-colored 
precipitate  with  ammonium  sulphide.  The  precipitate  is 
then  filtered,  boiled  with  hot  water,  and  the  combined  fil- 
trates treated  hot  with  carbonic  acid  until  neutral.  The 
barium  dithionate  crystallizes  from  the  filtrate  on  concen- 
tion. 

Dithionic  Acid.  —  59  grams  barium  dithionate  are  dis- 


100  LABORATORY    MANUAL    OF 

solved  in  water ;  20  grams  of  a  solution  of  sulphuric  acid 
diluted  with  water  are  added  to  the  solution  until  it  will  no 
longer  react  either  with  sulphuric  acid  or  with  barium  chlo- 
ride. After  filtering  off  the  barium  sulphate  the  dithionic 
acid  is  concentrated  on  a  flat  porcelain  plate  in  vacuum 
over  sulphuric  acid  to  a  sp.  gr.  of  1.347. 

The  peroxide  withdraws  from   2  molecules  of  sulphur- 

cr~\     rr 

ous  acid  two  atoms  of  hydrogen  ;  2HSO3H — 2H  =  ^Q3  j 

The  manganese  salt  of  the  dithionic  acid  is  decomposed 
by  the  excess  of  baryta  water. 

MnS3O6  +  Ba(OH)2=  BaS3O6  -f  Mn(OH)g. 

Barium  dithionate  forms  colorless,  glossy  crystals, 
which  in  a  powdered  condition  lose  their  water  of  crystal- 
lization (10.81  %)  at  100°  C. 

Determine  the  percentage  of  barium  oxide  (45.96  % 
BaO)  by  igniting  the  purified  salt  and  then  weighing  the 
residue  of  barium  sulphate. 


DISTILLED  MERCURY. 
Hg. 

In  a  combustion  furnace,  one  end  of  which  is  lifted 
15  mm.  above  the  other,  lay  a  tube  of  hard  Bohemian 
glass,  both  ends  of  which  are  bent  downward,  as  shown  in 
figure  8. 

The  end  drawn  out  is  connected  by  means  of  a  heavy 
walled,  closely  fitting  rubber  tube  with  a  glass  tube  of 
medium  thickness  about  10  mm.  outside  diameter,  and 
of  such  a  length  that  the  entire  vertical  tube  up  to  the 
lower  opening  which  turns  upward  is  about  700  mm.  The 


INORGANIC    PREPARATIONS. 


101 


giass  tube  stands  in  a  narrow  glass  cylinder.  The  other 
end  of  the  combustion  tube  is  bent  upward  somewhat 
within  the  furnace  so  that  the  last  flame  of  the  furnace 
stands  below  the  highest  point  *  of  the  bend  of  the  tube. 


FIG,  8. 

From  there  the  tube  leads  downward  20  cm.  without  re- 
duction in  size  ;  into  the  end  of  this  tube  by  means  of  a 
rubber  tubing, t  a  second  glass  tube  is  inserted,  bent  hook- 
form  at  the  bottom,  which  extends  at  least  5  cm.  into  the 
wider  tube,  and  is  about  80  cm.  in  length.  To  set  the 

*  At  the  point  of  the  tube,  place  a  loose  plug  of  asbestos. 

f  In  order  to  have  at  this  point  a  perfectly  airtight  connection,  add  the 
contrivance  pictured  in  the  small  illustration  on  the  right,  which  is  intellig- 
ible without  further  explanation.  The  small  space  ^surrounding  the  shaded 
part)  formed  by  a  rubber  stopper  and  a  small  pieci  of  wide  glass  tubing  is 
filled  with  mercury. 


102  LABORATORY    MANUAL   OF 

apparatus  in  motion  pour  into  the  cylinder  commercial 
mercury  or  else  mercury  which  has  become  impure  by  use 
with  other  metals,  and  exhaust  the  apparatus  with  a  filter 
pump,  adding  an  empty  Woulff  bottle.  As  soon  as  the 
mercury  has  risen  so  high  that  it  runs  along  in  a  thin 
stream  from  one  end  of  the  combustion  furnace  to  the 
other,  the  rubber  tubing  leading  to  the  pump  is  closed  se- 
curely with  a  pinch-cock.  Now  the  furnace  is  heated  with 
a  low  flame  while  the  mercury  boils  gently  and  distills 
through  the  asbestos  plug.  As  soon  as  the  tube  leading 
downward  is  filled  half  way  with  mercury,  open  the  pinch- 
cock  and  carefully  allow  air  to  enter  the  exhausted  tube ; 
the  mercury  column  now  prevents  air  from  entering  this 
side  of  the  apparatus.  The  apparatus  works  automatically, 
and  the  distilling  mercury  flows  continually  into  a  vessel 
placed  below ;  from  time  to  time  the  quantity  of  mercury 
in  the  cylinder  is  replaced. 

The  mercury  should  be  13.595  SP-  Sr-  at  °°  C.  and 
possess  a  pure  silver  gloss,  fuse  easily,  and  in  pouring  out, 
form  round  regular  drops  leaving  no  threadlike  residue. 
5  grams  heated  in  a  porcelain  crucible  should  not  leave  a 
weighable  and  fusible  residue. 


PURIFICATION  OF  MERCURY. 

Mercury  can  be  completely  freed  from  lead,  zinc,  tin, 
and  other  impurities  by  placing  it  in  a  slightly  inclined 
glass  tube  provided  with  a  funnel  at  the  lower  extremity, 
and  aspirating  a  gentle  stream  of  air  through  the  apparatus 
for  about  48  hours.  The  oxides  of  the  metals  collect  at 
the  upper  end.  of  the  tube,  and  after  about  24  hours,  as  a 


INORGANIC   PREPARATIONS.  IO3 

rule,  the  surface  of  the  mercury  is  quite  clean  and  the 
operation  is  finished.  Large  quantities  can  be  treated  in 
this  way,  but  mercury  which  has  been  used  for  amalgamat- 
ing zinc  contains  such  a  large  amount  of  impurity  that  this 
method  cannot  be  used.  Silver  is  not  removed  by  this 
process. 

Mercury  is  usually  purified  by  shaking  in  a  topped 
separator  with  cone,  sulphuric  acid,  allowing  time  to 
settle  and  drawing  off,  continue  until  the  mercury  is  bright 
and  no  longer  imparts  a  color  to  the  mercury.* 


MERCURIC    CHLORIDE, 

HgClg.    (FROM  RESIDUES.) 

The  residues,  oxydized  with  crude  hydrochloric  and 
nitric  acids  and  then  dried  on  the  water  bath  are  subjected 
to  slow  sublimation  in  a  porcelain  dish  on  a  sand-bath  with 
a  large  funnel  set  over  it.  Of  the  sublimate  thus  obtained 
dissolve  according  to  its  purity  i-io  to  1-5  in  hot  water, 
precipitate  with  soda  lye,  and  grind  the  so  obtained  mer- 
curic oxide  after  washing  and  drying  with  the  main  quan- 
tity of  the  sublimate  The  acquired  powder  which  turns 
black  through  the  formation  of  mercuric  oxychloride,  is 
placed  into  a  flask,  covered  loosely  with  a  watch  glass  and 
heated  on  the  sand  bath  over  a  small  flame.  The  subli- 
mate gathers  at  the  upper  part  of  the  flask  in  fine  long 
crystals.  After  final  sublimation  remove  the  flask  from 
the  bath,  break  off  the  bottom  by  quickly  passing  over  it 
a  damp  sponge  and  separate  the  crystals  from  the  glass  on 
a  large  sheet  of  paper  with  the  aid  of  a  goose  quill.  In 


*J.  M.  CRAFTS,  Bull.  Soc.  Chim.  49,  856. 


104  LABORATORY    MANUAL   OF 

case  there  are  poor  crystals  among  them,  they  are  to  be 
recrystallized  in  four  parts  of  boiling  water. 

The  crude  sublimate  is  contaminated  by  other  unstable 
metallic  chlorides,  but  these  are  all  decomposed  by  mer- 
curic oxide  ;  for  instance  :  Fe3Cle-f  3HgO  =  Fe2O3+  3HgCl2. 

Pure  white,  rhombic  prisms  of  mercuric  chloride  dis- 
solve readily  without  residue  (calomel,  iron  oxide,  etc.)  in 
cold  alcohol,  ether  and  hot  water  ;  heated  in  a  test  tube 
volatilize  without  residue. 


MERCURIC     CYANIDE. 

Hg(CN)2. 

A  diluted  prussic  acid  solution  is  mixed  in  a  flask  with 
yellow  mercuric  oxide  until  the  solution  reacts  strongly 
alkaline  to  litmus  paper.  Filter  and  add  to  the  filtrate 
enough  prussic  acid  to  make  the  odor  of  it  noticeable  and 
so  that  the  filtrate  will  react  distinctly  acid,  then  evaporate 
to  crystallization.  Before  the  mother  liquor  is  again  evap- 
orated to  crystallization,  add  a  little  more  prussic  acid. 

Mercuric  cyanide  crystallizes  in  square  columns  and 
pyramids  soluble  in  1 1  parts  of  cold  water  and  have  a 
neutral  reaction.  Heated  in  small  tubes,  the  salt  develops 
cyanogen,  gives  a  destillate  of  niercury  drops  and  leaves 
black  paracyanogen. 


CINNABAR. 

HgS. 

60  grams  mercury  are   intimately  mixed   in  a  mortar 
with  23  grams  flowers  of  sulphur   until  the  mercury  has 


INORGANIC    PREPARATIONS.  105 

entirely  disappeared.  Pour  over  this  a  solution  of  15 
grams  caustic  potash  in  80  c.  c.  water  and  digest  several 
days  at  about  45°  C.,  stirring  frequently  and  replacing  the 
evaporated  water.  After  the  mass  has  become  of  a  nice 
red  color,  it  is  separated  from  the  unaltered  mercury  and 
the  largest  part  of  the  sulphur  by  elutriation,  boiled  with  a 
solution  of  sodium  sulphite,  and  washed  with  hot  water. 

Cinnabar    is    a    scarlet-red   powder   and    when  heated 
strongly  in  small  tubes  volatilizes  without  residue. 


MERCUROUS     NITRATE 
Hg3(  N  O3)3  crystallized  +  2  H3O . 

Pour  I  part  of  pure  nitric  acid  of  1.2  sp.  gr.  on  I 
part  of  pure  mercury  in  a  porcelain  dish,  and  let  the  vessel 
stand  twenty-four  hours  in  a  cool  place ;  separate  the 
crystals  formed  from  the  undissolved  mercury  and  the 
mother  liquor,  and  dissolve  them  in  water  mixed  with  one- 
sixteenth  part  of  nitric  acid,  by  trituration  in  a  mortar. 
Filter  the  solution,  and  keep  the  filtrate  in  a  bottle  with 
some  metallic  mercury  covering  the  bottom  of  the  vessel. 

The  solution  of  mercurous  nitrate  must  give  with  di  - 
lute  hydrochloric  acid  a  copious  white  precipitate  of  mer- 
curous chloride ;  hydrogen  sulphide  must  produce  no  pre- 
cipitate in  the  fluid  filtered  from  this,  or  at  all  events,  only 
a  trifling  black  precipitate  (mercuric  sulphide). 


106  LABORATORY    MANUAL   OF 

MERCUROUS    IODIDE. 

Hg2I3 

If  a  saturated  solution  of  mercurous  nitrate  as  free  as 
possible  from  oxide  and  slightly  acidified  with  nitric  acid, 
is  heated  to  boiling  with  iodine,  the  latter  becomes  covered 
with  a  yellow  powder,  which  partially  dissolves,  and  the 
solution,  after  decantation  into  a  warm  dish,  deposits  in  the 
dark,  lustrous  yellow,  transparent,  tetragonal  scales  of 
mercurous  iodide  ;  these  must  be  dried  in  the  dark  at  or- 
dinary temperature.  When  the  mercurous  nitrate  solution 
is  treated  with  an  alcoholic  solution  of  iodine  in  the  cold, 
small,  yellow  spangles  of  mercurous  iodide  are  obtained, 
but  the  product  formed  by  the  old  methods  of  preparation, 
by  rubbing  together  molecular  proportions  of  mercury  and 
iodine,  and  adding  potassium  iodide  in  solution  to  a  solu- 
tion of  mercurous  salt,  have  a  green  color,  and  are  impure, 
although  the  pure  yellow  compound  can  be  obtained  by 
reversing  the  last  process,  and  adding  an  excess  of  a  dilute 
solution  of  mercurous  nitrate  to  potassium  iodide  in  solu- 
tion. The  crystallized  compound  shows  the  usual  color 
change,  yellow  at  100°  C.  passing  through  orange  to  gar- 
net-red at  higher  temperatures.  Sublimation  commences 
at  1 10  to  120°  C.  and  the  salt  fuses  at  290°  C.  without  de- 
composition. Towards  acids  and  solvents,  the  crystallized 
compound  behaves  like  that  precipitated  by  potassium 
iodide  ;  ammonia  and  caustic  alkalies  render  it  green,  and 
on  heating  convert  it  into  the  corresponding  alkaline  iodide 
and  metallic  mercury.  The  crystallized  iodide  is  less 
sensitive  to  light  than  the  precipitated  yellow  compound, 
which  rapidly  becomes  black  even  in  diffused  daylight.* 
*  A.  STROMAN,  Ber.  20,  2818. 


INORGANIC    PREPARATIONS.  1 07 


MERCUROUS    BROMIDE. 

Hg2Br3. 

When  mercurous  nitrate  solution  is  treated  with  bro- 
mine under  similar  conditions,  small,  white,  nacreous, 
tetragonal  scales  of  mercurous  bromide  are  obtained,  and 
the  same  compound  separates  in  yellow,  crystalline  span- 
gles when  an  alcoholic  or  aqueous  solution  of  bromine  is 
used.  It  sublimes  at  171°  to  176°  C.  in  small  scales,  is  less 
sensitive  to  light  than  the  iodide,  dissolves  in  hot  sulphuric 
acid  with  the  evolution  of  sulphurous  anhydride  becomes 
black  and  gradually  decomposes  when  heated  with  dilute 
and  concentrated  hydrochloric  acid,  dissolves  slowly  in  hot 
nitric  acid  (sp.  gr.  1.42),  and  decomposes  with  the  forma- 
tion of  the  corresponding  bromides  when  treated  with  am- 
monia and  caustic  alkalies. 


BORON. 

B. 

100  grams  fused  hot  finely  powdered  borax  are  well 
mixed  with  50  grams  magnesium  powder,  the  mass  poured 
in  a  Hessian  crucible,  pressed  down  well  and  covered  with 
a  layer  of  pure  borax.  All  these  operations  must  be  done 
rapidly  and  are  to  be  carried  on  in  warmed  vessels,  as  the 
anhydrous  borax  is  very  hygroscopic.  The  crucible  is 
closed  with  a  specially  well-fitting  cover  of  strong  sheet-iron 
with  a  rim,  and  heated  in  a  Roessler's  furnace  for  half  an 
hour  up  to  red  heat.  After  cooling,  grind  the  product, 
boil  it  with  water,  then  with  hydrochloric  acid  artd  finally 


108  LABORATORY    MANUAL    OF 

again   with   water   and  dry  the  grayish-brown   powder  on 
the  water-bath.* 

PREPARATION  OF  AMORPHOUS  BORON. 

Another  method  is  to  pass  a  current  of  35  amperes 
through  boric  anhydride  mixed  with  20  per  cent,  of  sodium 
borate  and  heated  at  1200°,  boron  is  liberated,  but  im- 
mediately recombines  with  oxygen  with  vivid  incan- 
descence. 

It  is  well  known  that  when  boric  anhydride  is  heated 
with  the  theoretical  quantity  or  an  excess  of  magnesium, 
reduction  takes  place  with  formation  of  magnesium  borides. 
If  the  boric  anhydride  is  in  considerable  excess  different 
results  are  obtained.  There  are  two  magnesium  borides, 
one  unstable  and  decomposed  by  water  with  liberation  of 
hydrogen  and  boron  hydride,  the  other  stable  and  not  af- 
fected by  water,  hydrochloric  acid,  or  nitric  acid. 

70  grams  of  finely  powdered  magnesium  free  from  iron 
and  silicon,  are  intimately  mixed  with  210  grams  of  re- 
cently fused  boric  anhydride.  The  mixture  is  heated  to 
bright  redness  in  a  clay  crucible,  and  in  a  few  minutes  an 
energetic  reaction  takes  place.  The  central  part  of  the 
product  is  boiled  with  water  and  hydrochloric  acid  until 
the  magnesium  borate  is  removed,  then  treated  for  a  long 
time  with  successive  quantities  of  pure  boiling  hydro- 
chloric acid,  washed  with  water,  treated  with  alcoholic 
potash,  again  washed  with  water,  boiled  for  several  hours 
with  hydrofluoric  acid,  washed  with  water,  and  dried  in  a 
vacuum.  The  product  is  a  very  light  maroon  powder 
which  does  not  alter  when  exposed  to  air ;  it  contains  94  to 


*  GATTERMANN,  Ber.  22,  195. 


INORGANIC    PREPARATIONS.  109 

95  per  cent,  of  boron,  2.3  to  3.75  per  cent,  of  magnesium 
and  1.2  to  1.6  per  cent  of  insoluble  matter. 

If  this  product  is  fused  with  50  times  its  weight  of  boric 
anhydride,  and  the  product  treated  in  the  same  way  as  the 
original  product,  a  maroon  powder  is  obtained  containing 
only  traces  of  magnesium. 

One  product  contained  boron,  98.30 ;  magnesium,  0.37; 
insoluble,  1.18  =  99.85. 

If  the  boron  is  required  perfectly  free  from  nitride,  re- 
duction must  be  affected  in  a  crucible  brasqued  with  a  mix- 
ture of  finely  powdered  titanic  oxide  and  carbon  ;  the 
product  contains  from  92.6  to  99.2  per  cent,  of  boron. 
Boric  anhydride  may  also  be  reduced  by  magnesium  in 
porcelain  dishes  in  an  atmosphere  of  hydrogen,  and  a  very 
pure  product  obtained,  but  the  yield  is  small.* 

It  can  also  be  prepared  by  mixing  3.5  grams  of  boric 
anhydride  and  1 1  grams  of  calcium  fluoride  by  gently 
heating  with  cone,  sulphuric  acid  ;  the  boron  fluoride 
evolved  is  passed  over  heated  potassium  contained  in  a 
series  of  bulbs.  Potassium  fluoride  and  boron  are  formed 
and  easily  separated  by  washing  with  water.  Amorphous 
silicon  may  be  prepared  in  a  similar  manner.t 

BORAX. 

Na2B4O7. 

An  intimate  mixture  of  well-ground  common  salt  and 
boric  acid  is  introduced  into  an  acid-proof,  tubulated  clay 
retort,  and  heated  to  slightly  above  a  low  red  heat,  when 
sufficient  superheated  steam  is  admitted  through  the  tu- 

*  By  H.  MOISSAN,  Compt.  rend.,  114,  392-397. 
f  S.  G.  RAVVSON,  Chem.  News,  58,  283. 


110  LABORATORY    MANUAL   OF 

bulature  to  condense  the  hydrochloric  acid,  which  is  evolved, 
the  acid  being  collected  in  a  cooled  receptacle  attached  to 
the  retort  neck.  Ultimately  anhydrous  borax  only  is  left 
in  the  retort,  and  this  is  thrown,  while  still  hot,  into  cold 
water  and  crystallized.* 


BOR  ACIC     ACID. 
H3B03. 

200  grams  powdered  borax  are  dissolved  in  one-half 
litre  of  boiling  water,  and  300  c.  c.  dil.  hydrochloric  acid 
added.  After  expiration  of  a  day  suck  the  separated  scaly 
crystals  dry  on  the  platinum  cone,  wash  them  with  a  very 
little  water,  and  recrystallize  once  from  water. 

The  white,  pearl-like  crystals  must  dissolve  in  6  parts 
alcohol  and  25  parts  cold  water  and  on  heating,  after 
evaporation  of  the  water,  melt  to  a  colorless  glass  which 
when  cooled  remains  transparent.  The  watery  solution 
reddens  litmus  paper  ;  if  turmeric  paper  strips  are  saturated 
with  it  and  dried  in  a  warm  place,  the  yellow  color  will  be 
changed  to  an  orange-brown,  which  with  alkaloids  be- 
comes greenish-black.  The  impurities  usually  present  are 
hydrochloric  and  sulphuric  acids. 


SILICON. 

Si 

Amorphous  silicon  is  readily  obtained  by  the  action  of 
magnesium  on  silica,  provided  that  the  materials  are  quite 
dry,  and  that  the  action  is  moderated  by  the  presence  of 
magnesium  oxide.  In  absence  of  the  oxide,  the  tempera- 

*  By  H.  N.  WARREN,  Chern.  News,  67,  244-245 


INORGANIC    PREPARATIONS.  Ill 

ture  of  the  reaction  is  too  high,  and  some  of  the  silicon  is 
fused.  Silica  is  not  so  satisfactory  as  magnesia  for  this 
purpose.  Powdered  quartz  and  magnesium  powder  such 
as  is  used  for  photographic  purposes  are  mixed  in  the  cal- 
culated proportions,  and  to  the  mixture  is  added  one-fourth 
of  its  weight  of  calcined  magnesia.  The  three  substances 
are  very  intimately  mixed  and  placed  in  a  fire  clay  cruci- 
ble, which  they  must  not  more  than  half  fill.  A  layer  of 
magnesia  is  placed  on  the  top,  and  the  crucible  is  then 
heated  at  149  to  205  p  C.  in  order  to  thoroughly  dry  the  con- 
tents. The  crucible  with  its  cover  is  then  heated  to  red- 
ness for  a  few  minutes,  and  as  soon  as  the  action  ceases  it 
is  allowed  to  cool.  Reduction  takes  place  at  282°  C.  If 
the  mixture  is  placed  on  a  plate  and  covered  with  mag- 
nesium powder,  and  the  latter  is  ignited,  reduction  spreads 
throughout  the  mass. 

The  product  is  heated  with  hydrochloric  acid,  then 
with  boiling  sulphuric  acid,  then  two  or  three  times  alter- 
nately with  hydrofluoric  acid  and  sulphuric  acid,  and, 
finally,  with  hydrochloric  acid.  After  drying,  the  silicon 
forms  a  maroon  colored,  homogeneous  powder,  containing 
only  i.o  to  0.4  per  cent,  of  impurities.  Any  small  globules 
of  fused  silicon  can,  if  necessary,  be  removed  by  levigation.* 

Another  method  is  to  heat  40  grams  of  finely  pow- 
dered sand  with  10  grams  of  magnesium  in  not  too 
thin  a  test  tube,  the  whole  tube  is  heated  first  mod- 
erately, and  then  a  small  portion  is  heated  strongly, 
beginning  at  the  lower  end  and  continuing  up- 
wards. The  product  is  grayish-black.  The  frag- 
ments of  the  tube,  after  the  substance  has  been  taken  out, 

*  By  VIGOURON,  Compt.  rend.,  iScjs,  120,  94. 


112  LABORATORY    MANUAL    OF 

should  be  treated  with  acid,  as  the  adherent  substance  will 
decompose  in  moist  air  and  evolve  silicon  hydride.  Silicon 
is  obtained  by  heating  the  substance  in  a  closed  crucible 
with  zinc  ;  on  dissolving  out  the  zinc,  it  is  obtained  in  steel- 
btoe  needles.* 

It  can  also  be  prepared  by  introducing  aluminium, 
in  pieces  the  size  of  a  walnut,  into  a  clay  crucible 
containing  a  fused  mixture  of  4  parts  of  potassium 
silico-fluoride,  I  part  of  potassium  chloride,  and  2 
parts  of  potassium  carbonate,  and  when  the  violent 
reaction  has  subsided,  the  mass  is  heated. to  whiteness  for 
five  minutes.  When  cool,  the  crucible  is  smashed  ;  the 
button,  carefully  detached  from  adhering  slag,  is  placed  in 
a  plumbago  crucible  with  12  parts  by  weight  of  aluminium 
and  2  of  tin,  and  covered  with  a  layer  of  sodium  silicate, 
the  mixture  is  submitted  for  two  hours  to  the  strongest 
heat  obtainable.  When  cold,  the  piece  of  aluminium  is 
broken,  when  the  new  modification  of  silicon  is  found  in 
large,  lustrous,  infusible,  oblique  octahedra,  insoluble  in  all 
acids  except  hydrofluoric.! 

Still  another  method  is  as  follows :  Small  bars  of 
"  silicon-eisen  "  are  suspended  in  dilute  sulphuric  acid 
from  the  positive  pole  of  a  battery  of  two  ferric 
chloride  cells  and  are  in  contact  with  a  platinum 
plate  forming  the  negative  pole.  The  iron  dissolves  and 
leaves  a  residue  of  graphite,  silica,  and  amorphous  silicon, 
which  is  heated  to  redness  in  a  stream  of  carbonic  an- 
hydride, and  then  to  a  full  red  heat  in  a  closed  iron 
tube  with  some  zinc ;  the  zinc  button  obtained  in  this 


*L.  GATTERMANN,  Ber.  22,  186. 

f  By  H.  N.  WARREN,  Chem.  News,  67,  136-137. 


INORGANIC    PREPARATIONS.  113 

manner  is  dissolved  in  hydrochloric  acid,  when  crystal- 
line silicon  remains  insoluble ;  by  heating  the  amor- 
phous silicon  at  a  full  white  heat  with  aluminium  instead 
of  zinc,  graphitoidal  silicon  is  obtained.  When  an  alloy 
of  aluminium  and  silver  is  heated  to  an  intense  white 
heat  with  potassium  silicofluoride,  small  quantities  of 
silicon  are  produced  in  the  form  of  a  bright  reddish- 
brown  powder.* 

CRYSTALLINE  SILICIC    ACID. 
H2Si03. 

Silicious  limestone  is  treated  with  crude  concentrated 
hydrochloric  acid  until  carbonic  anhydride  ceases  to  be 
evolved,  filter  and  add  to  the  filtrate  29  to  31  per  cent, 
hydrochloric  acid  until  a  cloudiness  appears.  After  re- 
maining 24  hours  the  solution  is  decanted,  the  precipi- 
tate strained  and  washed,  finally  with  distilled  water  and 
then  dried  on  porcelain.  Silicic  acid  so  obtained  is 
crystalline  and  corresponds  to  the  formula  H2SiO3  +  3H2O 
or  H2SiO3+2H2O.  It  is  more  soluble  than  the  amor- 
phous variety.! 

SILICON    CHLORIDE. 

SiCl4. 

Take  a  hard  glass  tube  2  m.m.  wide,  fill  it  half  way 
with  the  crude  amorphous  silicium  as  described  above, 
lay  it  horizontally  in  a  combustion  furnace  and  at  mod- 
erate heat,  lead  a  current  of  dry  chlorine  over  it. 


*  II.  N.   WARREN,    Chem.   News,   57,  54. 
f  H.  HAGER,  Pharm.  Centralb.  29,  115.  /'    ^ 


ITY  '' 


114  LABORATORY    MANUAL    OF 

The  distilling  silicon  chloride  is  condensed  in  a  receiver 
which  is  surrounded  by  a  freezing  mixture  of  ice  and  com- 
mon salt,  while  the  surplus  chlorine  is  absorbed  in  soda 
lye.  The  greenish  product  is  shaken  with  a  little  mercury, 
and  then  distilled  from  the  water- bath  with  a  thermome- 
ter and  condenser  attached. 

Si  -f 4C1  =  SiCl4.     The   free   chlorine   dissolved    in    the 
silicon  chloride  is  removed  by  shaking  with  mercury. 

The  silicon  chloride  should  boil  at  58  to  60°  C.  and 
appear  as  a  colorless,  mobile  liquid  fuming  strongly  when 
exposed  to  the  air,  it  is  decomposed  by  water  with  separa- 
tion of  hydrated  silicic  acid  : 

SiCU  +  4H30  =  Si(OH)4  +  4HC1. 


CHLORIDES    OF    SILICON,    ALUMINIUM,    ETC. 

Iron  alloys  of  silicon  or  aluminium  are  heated  to  red- 
ness in  a  clay  crucible,  and  a  current  of  chlorine  gas  is 
passed  into  the  mass,  suitable  means  being  adopted  to  col- 
lect the  volatile  products.  With  chlorine  and  silicon-iron, 
the  ferric  chloride  is  condensed  first,  then  the  silicon 
chloride  ;  if  hydrogen  chloride  is  used  instead  of  chlorine, 
the  ferrous  chloride  formed  remains  in  the  crucible  and 
silicon  chloroform  distills  off.  The  aluminium  chloride  ob- 
tained from  aluminium  iron  is  purified  by  mixing  with  iron 
borings  and  distilling,  or  if  the  aluminium  iron  alloy  is 
mixed  with  common  salt  previous  to  submitting  it  to  the 
action  of  chlorine,  a  sublimate  of  aluminium  sodium 
chloride  is  obtained. 


*By  H.  N.  WARREN,  Chem.  News,  60,  158. 


INORGANIC    PREPARATIONS.  115 


PREPARATION   OF   SILICON  AND  ALUMINIUM 
CHLORIDE. 

Silicon  chloride,  mixed  with  but  little  ferric  chloride 
and  readily  purified  by  redistillation,  is  obtained  by  pass- 
ing chlorine  'into  siliconeisen,  containing  15  per  cent,  of 
silicon,  heated  to  redness  in  a  tubulated  clay  retort,  and 
retaining  the  less  volatile  ferric  chloride  in  the  upper 
part  of  a  suitable  adapter,  while  the  lower  part  is  cooled 
in  a  freezing  mixture  to  condense  the  silicon  chloride.  By 
using  hydrochloric  acid  gas  instead  of  chlorine,  ferrous 
chloride,  and  the  more  volatile  silicon-chloroform,  SiHCl3, 
are  obtained. 

By  the  action  of  chlorine  on  an  alloy  of  iron  with  10 
per  cent,  of  aluminium,  aluminium  chloride  is  produced, 
which  can  be  purified  by  distillations  from  iron  borings. 
When  the  pulverized  alloy  is  previously  mixed  with  sodium 
chloride,  the  passage  of  chlorine  gives  rise  to  the  sublima- 
tion of  aluminium  sodium  chloride. 


ALUMINIUM     HYDRATE. 

Al3(OH)e,//w»  Cryolite. 

50  grams  cryolite  are  finely  powdered,  then  thoroughly 
mixed  with  50  grams  calcined  marble  and  ignited  for  half  an 
hour  in  a  platinum  crucible  placed  in  Roessler's  furnace. 
The  powdered  melt  is  boilecl  with  water,  possible  traces  of 
calcium  removed  from  the  filtered  solution  by  a  few  drops 
of  soda  solution  and  then  precipitated  hot  with  carbonic 


*  H.  N.  WARREN,  Chem.  News,  66,  113-114. 


Il6  LABORATORY    MANUAL    OF 

acid.  The  separated  aluminium  hydrate  is  washed  by  de- 
cantation  with  a  good  deal  of  hot  water,  collected,  dried 
on  the  water  bath,  and  if  desired,  transformed  into  an- 
hydrous aluminium  sesquioxide  by  ignition.  The  filtrate 
when  evaporated,  leaves  pure  sodium  carbonate. 

The    aluminum    sodium  fluoride    is    decomposed    by 
caustic  lime,  forming  sodium  aluminate  soluble  in  water: 

NadAl3Fi2  +  6CaO  =  Na6Al3O6  +  6CaF3. 
The  sodium  aluminate  is  decomposed  by  carbonic  acid  : 
2Na6Al2O6  +  6H3CO3  =  2A13(OH)6  +  6Na3CO3. 


REDUCTION    OF    ALUMINIUM    OXIDE. 

A12O3. 

Two  parts  of  pure,  finely  powdered  aluminium  oxide 
is  made  into  a  paste  with  one  part  of  petroleum  or  some 
other  hydro-carbon,  and  then  mixed  with  one  part  of  sul- 
phuric acid.  When  the  mass  is  homogeneous  with  a  pale 
yellow  tint,  and  begins  to  give  off  sulphurous  anhydride,  it 
is  wrapped  in  paper  and  thrown  into  a  crucible  heated  to 
above  800°  C.  in  order  to  decompose  the  hydrocarbon.  The 
compact  product  thus  obtained  is  powdered  and  mixed 
with  its  own  weight  of  a  finely  divided  metal,  the  mix- 
ture being  then  heated  to  a  white  heat  in  a  plumbago 
crucible.  The  regulus  after  being  allowed  to  cool  is  found 
to  contain  grains  of  an  aluminium  alloy  in  the  midst  of  a 
metallic  powder.  This  method  of  reduction  is  applicable 
to  silica,  calcium  oxide,  magnesium  oxide,  etc.* 


G.  A.  FAURIE,  Compt.  Rend.  105,  494. 


INORGANIC    PREPARATIONS. 


ANHYDROUS    ALUMINIUM  CHLORIDE. 

AloCl6. 

Dry  hydrogen  chloride  extracts  the  whole  of  the  alum- 
inium from  an  alloy  of  copper  and  aluminium  without  at- 
tacking the  copper.  The  reaction  is  most  energetic  a 
little  below  a  red  heat.  The  alloys  containing  15  to  40 
per  cent,  of  aluminium  are  best  powdered,  mixed  with 
powdered  charcoal  (to  prevent  the  fusion  of  the  remaining 
copper),  put  into  a  graphite  retort,  and  when  heated  just 
below  a  red  heat  a  current  of  hydrogen  chloride  is  passed 
through.  The  aluminium  chloride  distills  over,  and  may 
be  condensed  in  suitable  vessels,  the  liberated  hydrogen 
passing  on. 


FORMATION  OF  ULTRAMARINE  IN  THE 
WET  WAY. 

The  material  used  is  washed  kaolin,  with  the  fol- 
lowing percentage  composition:  Silica,  46.83;  alumina, 
40.25;  water,  12.60;  potash,  0.37;  lime,  trace;  total, 
100.05  ;  and  was  expressed  by  the  formula: 

2SiO3:  1.997  A13O3  ::  1.79  H2O. 

The  ultramarine  mixture  is  made  in  the  proportion — 
Washed  kaolin,  IOO  parts  ;  anhydrous  sodium  carbonate, 
IOO  parts;  sulphur,  60  parts.  The  mixture  is  heated  in 
small  porcelain  crucibles,  holding  15  to  20  grams  of  the 
mixture;  this  is  pressed  in,  and  the  top  covered  to  a 


*  By  C.  F.  MABERY,  Ber.  22,  2658. 


Il8  LABORATORY    MANUAL    OF 

depth  of  5  to  6  mm.  with  powdered  charcoal,  and  the  cruci- 
ble then  heated  with  the  lid  on.  The  mixture,  after  heat- 
ing and  separation  from  the  charcoal,  gives  on  digestion 
with  solution  of  liver  of  sulphur,  the  deep  blue  of  ultra- 
marine. Kaolin,  digested  alone  with  liver  of  sulphur  solu- 
tion, is  unchanged.* 


HYDROGEN    BROMIDE. 
HBr. 

100  grams  benzole  and  a  few  grams  of  anhydrous  fer- 
rous bromide  are  placed  in  a  dry  two-necked  bottle  and 
135  c.  c.  bromine  allowed  to  drop  in  from  a  dropping  fun- 
nel with  long  fine  stem.  The  Woulff  bottle  is  placed  in 
cold  water  during  the  first  half  of  the  operation,  in  order 
to  control  the  vigorous  heating  and  volatilization  of  the 
benzole  which  takes  place.  The  gas  is  passed  through  a 
small  tube  charged  with  anhydrous  ferrou.  bromidef  then 
through  one  charged  with  anthracene  and  now  forms  pure 
hydrogen  bromide.  For  the  production  of  cone,  aqueous 
hydrobromic  acid,  the  gas  is  led  into  a  small  bottle,  by  de- 
grees small  quantities  of  water  are  added  with  a  wash-bot- 
tle and  cooled  with  a  freezing  mixture  of  ice  and  common 
salt.  The  saturated  solution  is  preserved  in  a  well  stoppered 
bottle  with  cap  and  kept  in  a  dark  place. 

C6H6  +4Br  =  C6H4Br2  +  2HBr. 
The  small  quantity  of  ferrous  bromide  (FeBr3)  acts  as 


*  By  F.  KNAPP,  J.  pr.  Chem.  [2]  32,  375-39O- 

f  Produced  by  mixing  25  grams  ferrous  FeBr,  bromide  with  3  c.  c.  bro- 
mine in  the  cold. 


INORGANIC    PREPARATIONS.  IIQ 

the  transferrer  of  bromine.  The  hydrogen  bromide,  devel- 
oped in  a  very  regular  stream,  carries  off  benzole-vapors 
which  bromate  in  the  ferrous  bromide  tube  and  are  held 
back.  The  gas  is  freed  by  the  anthracene  from  the  slight 
traces  of  free  bromine. 

The  aqueous  solution  should  be  entirely  colorless,  fume 
strongly  when  exposed  to  the  air,  and  have  a  sp.  gr.  of  at 
least  1.78  (at  o°  C.  saturated  acid). 

Another  method  : — A  mixture  of  I  part  of  red  phos- 
phorus, 2  parts  of  water,  and  sufficient  sand  to  form  a 
paste,  is  introduced  into  a  flask,  10  parts  of  bromine  then 
gradually  added  by  means  of  a  funnel  provided  with 
a  stopcock,  the  flask  gradually  warmed,  and  the  mixture 
of  hydrogen  bromide  and  bromine  vapor  passed  through  a 
deep  glass  jar  filled  with  a  mixture  of  red  phosphorus  and 
asbestos,  impregnated  with  concentrated  hydrobromic  acid. 
Every  trace  of  bromine  vapor  is  thus  effectually  retained, 
and  the  process  is  continuous  and  requires  no  supervision 
beyond  an  occasional  shaking  of  the  flask.* 

By  means  of  the  following  arrangement,  a  large  quan- 
tity of  bromine  can  be  rapidly  converted  into  hydrobromic 
acid  :  A  glass  tube,  7  inches  long  and  ^  inch  in  diameter, 
is  fitted  at  each  end  with  a  cork  carrying  a  piece  of  small 
tubing  and  a  piece  of  stout  wire.  The  ends  of  these  pieces 
of  stout  wire,  within  the  longer  tube,  are  joined  by  a  spiral 
of  platinum  wire  I  inch  long,  and  after  expelling  the  air 
the  spiral  is  heated  to  bright  redness  by  an  electric  current ; 
a  stream  of  hydrogen,  impregnated  with  bromine  by  bub- 
bling through  that  liquid,  which  may  be  heated  at  60°  C.,  is 
passed  through  the  longer  tube,  and,  as  long  as  a  slight 


M.  FILETI  and  F.  CROSA,  Gazetta,  21,  64. 


I2O  LABORATORY    MANUAL   OF 

excess  of  hydrogen  is  maintained,  hydrobomic  acid  quite 
free  from  bromine  issues  from  the  other  end,  and  is  col- 
lected in  water.  There  is  very  little  danger  from  explo- 
sion, but  to  render  it  impossible,  the  small  supply  tube  may 
be  plugged  with  a  little  glass  wool* 

A  convenient  method  of  preparing  hydrogen  bromide 
in  quantity  is  to  drop  strong  sulphuric  acid  from  a  tap 
funnel  on  solid  potassium  bromide  heated  in  a  stoppered, 
tubulated  retort  on  the  water-bath.  The  gas  given  off  is 
contaminated  with  small  quantities  of  sulphurous  anhy- 
dride and  bromine,  from  which  it  is  freed  by  two  sets  of 
wash- bottles,  the  first  of  which  contains  a  strong  solution 
of  bromine  in  hydrobromic  acid,  the  second,  amorphous 
phosphorus  suspended  in  hydrobromic  acid.  When  all 
the  sulphuric  acid  has  been  added,  and  the  evolution  of 
gas  has  slackened,  the  retort  may  be  heated  over  a  flame. 

Another  method  is  to  pass  sulphurous  anhydride 
through  a  solution  of  bromine  (i  vol.)  in  concentrated 
hydrobromic  acid  (i  vol.).  The  evolved  hydrogen  bro- 
mide is  then  purified  as  above. t 

Hydrogen  bromide  may  also  be  prepared  by  adding 
bromine  (385  grams)  to  a  mixture  of  liquid  paraffin  (500 
grams)  and  dry  phosphorus  in  small  pieces  50  grams ; 
water  (about  100  grams)  is  then  gradually  run  in  and  the 
evolved  gas  purified  by  passage  over  moist  phosphorus.^ 

This  method,  proposed  for  the  preparation  of  hydro- 
bromic acid,  is  based  on  the  fact  that  the  action  of 
gaseous  hydrogen  sulphide  on  liquid  bromine  with  forma- 


*G.  S.  NEWTH,  Chem.  News,  64,  215. 
fE.  LEGER,  Compt.  rend.  115,  946-948. 
JA.  GASSMAN,  Chem.  Centr.  1893,   i.,  771- 


INORGANIC   PREPARATIONS.  121 

tion  of  gaseous  hydrogen  bromide  and  solid  sulphur  de- 
velops +  144  cal.,  without  taking  into  account  the  heat 
developed  by  the  combination  of  the  sulphur  with  the 
excess  of  bromine. 

Hydrogen  sulphide  is  bubbled  through  a  layer  of 
bromine  contained  in  a  tall,  narrow  vessel,  and  covered 
by  a  layer  of  water  or  hydrobromic  acid.  The  gas  passes 
into  a  second  flask  which  contains  a  solution  of  potassium 
bromide  in  hydrobromic  acid  holding  a  small  quantity  of 
red  phosphorus  in  suspension,  and  the  gas  which  issues 
from  this  flask  contains  neither  bromine  vapor  nor  hydro- 
gen sulphide.  The  current  of  hydrogen  bromide  is  con- 
trolled by  regulating  the  current  of  hydrogen  sulphide. 
The  latter  gas  should  be  made  in  a  "  continuous " 
apparatus.* 

Although  concentrated  sulphuric  acid  decomposes  po- 
tassium bromide  with  liberation  of  bromine,  when  a  more 
dilute  acid  is  used  there  is  no  evolution  of  bromine.  To 
obtain  pure  hydrobromic  acid,  150  c.  c.  of  sulphuric  acid 
of  1.41  sp.  gr.  is  poured  on  to  IOO  grams  of  coarsely  pow- 
dered potassium  bromide,  and  the  mixture  warmed  gently 
and  shaken  until  the  salt  is  dissolved.  The  liquid  is  then 
submitted  to  distillation  ;  it  begins  to  boil  at  about  126°  C., 
and  the  temperature  slowly  rises  to  150°  C.,  at  which  point 
almost  the  whole  of  the  hydrobromic  acid  passes  over;  then 
the  temperature  rapidly  goes  up  to  200°  C.,  and  traces  of 
sulphuric  acid  are  mechanically  carried  over.  The  process  is 
now  stopped,  as  between  200°  and  250°  C.  only  small  quan- 
tities of  hydrobromic  acid,  mixed  with  a  little  sulphuric 
acid,  pass  over.  The  distillate  is  redistilled,  collecting  only 


A.  RECOURA,  Compt.  rend.,  no,  784. 


122  LABORATORY    MANUAL    OF 

what  passes  over  at  1 26°  C.  ;  this  has  a  specific  gravity  of 
1.49,  contains  48  per  cent,  of  HBr,  is  colorless,  and  con- 
tains neither  sulphuric  acid,  sulphurous  acid,  nor  bromine. 
150  grams  of  bromide  yield  about  200  grams  of  acid.  If 
the  bromide  contains  bromate,  the  receiver  is  changed  when 
the  distillate  become  colorless  ;  the  acid  thus  obtained  con- 
taining bromine  is  treated  with  a  little  sodium  sulphite,  and 
rectified  with  the  rest.  Gaseous  hydrobromic  acid  may  be 
obtained  by  distilling  the  solution  containing  48  per  cent, 
from  anhydrous  calcium  bromide.* 


HYDROGEN     IODIDE. 
HI. 

In  preparing  hydrogen  iodide  from  iodine  and  amorphous 
phosphorus  the  iodine  is  placed  in  a  flask  provided  with  a 
bent  neck  and  connected  with  the  vessel  containing  the  phos- 
phorus and  water  by  means  of  a  bent  tube.  By  turning 
the  flask  round  the  bent  tube,  fresh  quantities  of  iodine 
can  be  added  when  requisite  without  admitting  air  into 
the  apparatus. t 

Another  method  of  preparation  is  to  moisten  100  parts 
of  iodine  contained  in  a  retort  with  about  10  parts  of  water. 
The  retort  is  then  fitted  with  a  funnel  closed  with  a  glass 
rod,  containing  5  parts  of  amorphous  phosphorus  mixed 
with  10  parts  of  water.  One  drop  of  water  containing  phos- 
phorus is  let  into  the  retort ;  more  phosphorus  is  slowly 


*By  W.  FEIT  and  K.   KUBIERSCHKY,   J.  Pharm.  [5],  24,  159;  from 
Pharm.  Zeit.  Russ.,  30,  298. 

f  A.  ETARD,  Bull.  Soc.  Chim.  49,  742. 


INORGANIC    PREPARATIONS.  123 

added,  after  which  large  amounts  may  be  used.  The  mix- 
ing is  complete  in  15  minutes.  If  more  than  a  drop  is 
added  at  first  the  action  cannot  be  controlled,  and  will 
generally  result  in  a  violent  explosion.  No  heating  is 
necessary.  The  iodine  carried  over  by  the  hydrogen 
iodide  is  nearly  all  deposited  in  the  neck  of  the  retort, 
which  is  inclined  upward.  By  using  100  grams  of  iodine, 
5  grams  of  phosphorus  and  25  c.  c  of  water,  95  grams 
of  hydrogen  iodide  (of  which  37.5  grams  were  obtained  by 
distillation)  are  obtained,  instead  of  100.8  grams.  With 
20  grams  of  water  98. 1  grams  are  obtained  (74.4  grams 
as  gas  and  23.7  grams  by  distillation).* 


IODINE    PENTOXIDE. 
I205. 

30  grams  iodine  are  placed  in  a  retort  and  158  c.  c. 
of  water  and  nitric  acid  free  from  nitrogen  oxides  (page  18) 
poured  over  it.  On  shaking  a  reaction  takes  place  which 
is  hastened  by  moderate  heating.  The  red  vapors  are 
driven  out  by  a  strong  current  of  air,  which  is  blown  into 
the  tubulature  of  the  retort  through  a  glass  tube.  In  spite 
of  this  a  part  of  the  iodine  is  invariably  reduced  by  these 
nitrogen  oxides ;  it  volatillizes  and  is  condensed  with  the 
distilling  acid  in  a  receiver,  which  is  kept  cool.  At  inter- 
vals the  heating  is  stopped  and  the  distillate,  after  having 
air  blown  into  it,  is  put  back.  The  white  residue  is  dis- 
solved in  a  little  water  and  evaporated  to  dryness  in  a 
porcelain  dish,  iodic  acid  anhydride  remaining  in  white 
crystals. 

*  H.  I.  L.  MEYER,  Ber.  20,  3381. 


124  LABORATORY    MANUAL   OF 


IODINE     TRICHLORIDE. 
IC13. 

20  grams  iodine  are  gently  heated  in  a  small  retort,  the 
bent  neck  of  which  terminates  in  a  weighed  balloon  filled 
with  chlorine  and  closed,  but  connected  with  a  Kipp's 
chlorine  apparatus.  As  soon  as  the  iodine  vapors  enter 
the  balloon  a  strong  absorption  of  chlorine  takes  place,  and 
iodine  chloride  precipitates  against  the  walls  in  reddish- 
yellow  crystals.  Finally  dry  carbonic  acid  is  led  through 
to  drive  out  the  surplus  chlorine.  Any  particles  which 
cannot  be  removed  from  the  balloon  mechanically  are  dis- 
solved in  ten  times  their  weight  of  water,  and  preserved  as 
iodine  chloride  solution. 

Iodine  trichloride  is  an  orange-colored  pungent  crys- 
talline powder,  readily  soluble  in  water  to  a  clear  yellow 
liquid.  Chloroform  should  not  remove  iodine  from  the 
aqueous  solution  until  a  little  stannous  chloride  has  been 
added.  On  heating,  the  iodine  trichloride  should  change 
without  leaving  any  residue  into  brown  vapors,  which  con- 
dense again  to  an  orange- colored  sublimate. 


HYDROCYANIC    ACID. 
HCN. 

500  grams  coarsely  powdered  potassium  ferricyanide  are 
distilled  on  the  gas  stove  in  a  well  ventilated  place,  with  a 
mixture  of  350  grams  cone,  sulphuric  acid  and  700  c.  c.  water. 
With  the  condenser  two  WoulfT  bottles  are  connected;  these 


INORGANIC    PREPARATIONS.  125 

stand  on  ice ;  the  vapors  escaping  from  the  last  bottle  are 
led  into  cold  water.  The  insoluble  residue*  forming  in  the 
retort  causes  a  slight  jolting  of  the  contents,  but  by  heat- 
ing uniformly  and  carefully  no  danger  need  be  feared. 
The  distillate  is  almost  pure.  If  absolutely  anhydrous 
hydrogen  cyanide  is  required,  fill  the  first  of  the  Woulfif 
bottles  before  distillation  half-way  with  porous  calcium 
chloride,  and  at  the  conclusion  set  it  in  warm  water,  in  order 
to  distill  its  contents  into  the  second  bottle.  The  product 
should  not  be  preserved  in  an  anhydrous,  but  in  a  diluted 
condition ;  the  aqueous  hydrocyanic  acid  keeps  still  better 
if  one  drop  of  diluted  mineral  acid  is  added  to  every  100 
c.  c. 

The  anhydrous  hydrocyanic  acid  is  a  very  volatile, 
colorless  liquid,  which  when  brought  in  contact  with  the 
skin  produces  a  cold  feeling,  like  evaporated  ether.  It 
boils  at  27°  C.  and  crystallizes  in  a  freezing  mixture.  The 
aqueous  solution  does  not  redden  litmus  paper,  t 


PURIFICATION    OF    HYDROFLUORIC    ACID. 

HF. 

The  apparatus  employed  for  distilling  commercial  hy- 
drofluoric acid  consists  of  a  heavy  sheet-lead  retort,  6  inches 
high  and  4  inches  in  diameter,  with  a  rim  at  the  top  formed 
by  beating  the  lead  over  an  iron  ring  i  inch  deep  and  ^ 
inch  thick  ;  the  lid  is  of  j£  inch  iron  plate,  covered  with 
lighter  sheet  lead,  and  is  fixed  down  by  a  screw  working  in 
a  socket  in  an  iron  bridge,  which  is  secured  to  projections 


*  This  residue  may  be  used  in  the  preparation  of  Berlin  Blue, 
f   WOHLER,  Annalen,  73,  219. 


126  LABORATORY    MANUAL    OF 

on  the  opposite  sides  of  the  iron  ring  of  the  rim.  A  washer 
of  india-rubber  is  placed  between  the  cover  and  the  rim. 
The  leaden  nose  of  the  retort  points  upwards,  and  is  con- 
nected by  india-rubber  tubing  to  a  Liebig  condenser,  the 
inner  tube  of  which  is  of  thin  india-rubber.  The  retort  is 
charged  through  a  funnel  with  25  per  cent,  hydrofluoric 
acid,  which  yields  a  distillate  of  convenient  strength  for 
analytical  work.  The  first  portions  of  the  distillate  con- 
tain silicate  and  are  discarded,  whilst  any  sulphur  is  re- 
moved by  filtration.* 


STANNOUS     CHLORIDE. 

SnCte,  Crystallized  +  2H2O. 

Reduce  grain  tin  to  powder  by  means  of  a  file,  or  by 
fusing  it  in  a  small  porcelain  dish,  removing  from  the 
fire,  and  triturating  with  a  pestle  until  it  has  passed  again 
to  the  solid  state.  Boil  the  powder  for  some  time  with 
concentrated  hydrochloric  acid  and  a  few  drops  of  platinic 
chloride  in  a  flask  (taking  care  always  to  have  an  excess  of 
tin  in  the  vessel)  until  hydrogen  gas  is  scarcely  evolved  ; 
dilute  the  solution  with  4  times  the  quantity  of  water 
slightly  acidulated  with  hydrochloric  acid,  and  filter.  Keep 
the  filtrate  for  use  in  a  well-stoppered  bottle  containing 
small  pieces  of  metallic  tin,  or  some  pure  tin-foil.  If  these 
precautions  are  neglected  the  stannous  chloride  will  soon 
change  to  stannic  chloride,  with  separation  of  white  oxy- 
chloride,  which  will  render  the  reagent  unfit  for  use. 


*  By  R.  HAMILTON,  Chem.  News,  60.  252. 


INORGANIC    PREPARATIONS.  I2/ 


A  solution  of  stannous  chloride  must,  when  added  to 
excess  of  solution  of  mercuric  chloride,  immediately  pro- 
duce a  white  precipitate  of  mercurous  chloride  ;  when  treated 
with  hydrogen  sulphide  it  must  give  a  dark  brown  pre- 
cipitate ;  it  must  not  be  precipitated  nor  rendered  turbid 
by  sulphuric  acid. 

ANHYDROUS    STANNOUS    CHLORIDE. 

SnCl2. 

Commercial  stannous  chloride  is  heated  slowly  on  the 
gas  stove  ;  the  salt  melts  in  its  water  of  crystallization,  then 
becomes  pasty,  and  gradually  entirely  solid.  The  dehy- 
drated salt  is  fused  once  more,  and  in  cooling  it  is 
placed  in  a  mounted  retort  of  hard  Bohemian  glass,  the 
upper  part  of  which  is  covered  with  a  cap  of  wire  gauze  or 
asbestos,  to  avoid  too  strong  radiation,  and  distilled  as 
quickly  as  possible  into  a  porcelain  dish,  which  is  kept 
covered  with  a  second  dish.  As  the  stannous  chlo- 
ride boils  at  about  327°  C.  the  heat  must  be  very 
strong  ;  a  small  blow-pipe  furnace  will  serve  as  the  best 
source  of  heat.  The  neck  of  the  retort  is  heated  with  a 
Bunsen  burner,  so  it  will  not  choke  up  with  the  solidifying 
distillate. 

Anhydrous  stannous  chloride  is  a  white,  crystalline 
mass,  melting  at  250°  C.,  dissolving  readily  in  water,  alcohol, 
ether  and  soda  lye. 

ANHYDROUS    STANNIC    CHLORIDE. 

SnCl4. 

150  grams  pure  tin  (granulated  or  in  bars)  are  heated 
to  fusion  on  the  gas  stove  in  a  mounted,  tubulated  retort, 


128  LABORATORY    MANUAL    OF 

and  a  strong  stream  of  dry  chlorine  led  into  it  through  a 
glass  tube  opening  near  the  surface  of  the  fused  metal. 
The  retort  connects  with  a  very  long  condenser  and  two 
Woulff  bottles  as  receivers.  The  receivers  are  placed  in 
ice-water,  to  hasten  the  condensation  of  the  very  volatile 
chloride.  The  chloride  collected  is  distilled  from  a  frac- 
tional distilling  flask  containg  a  little  tinfoil. 

Sn  +  4C1  =  SnCl4.  The  free  chlorine  combines  with 
the  metallic  tin  during  the  rectification. 

Anhydrous  stannic  chloride  is  a  colorless  solution, 
boiling  at  114°  C,  fuming  strongly  when  exposed  to  air, 
of  2.278  sp.  gr.  at  o°  C.,  with  a  small  amount  of  water,  it 
furnishes  crystalline  compounds,  but  dissolves  completely 
in  a  larger  quantity  of  water. 


PHOSPHORUS 

FROM 

PHOSPHATES  OF  THE  ALKALIES  AND  ALKA- 
LINE   EARTHS    BY    MEANS 
OF    ALUMINIUM. 

When  sodium  metaphosphate  is  heated  with  aluminium 
in  a  current  of  hydrogen,  28  to  31  per  cent,  of  the  phos- 
phorus distills  over,  and  a  residue  is  obtained  consisting  of 
alumina,  sodium  aluminate,  and  aluminium  phosphide.  All 
the  phosphates  of  calcium  and  magnesium,  when  heated 
with  aluminium,  yield  phosphorus. 

Aluminium  phosphide,  A1-P5  is  obtained  by  heating 
aluminium  in  phosphorus  vapor,  and  then  heating  the 
product  until  phosphorus  ceases  to  come  off.  It  is  a  gray 
crystalline  powder. 


INORGANIC    PREPARATIONS.  129 

The  whole  of  the  phosphorus  in  the  phosphates  may 
be  obtained  by  adding  silica  to  the  mixture  in  the  propor- 
tions represented  by  the  equation  : 

3Ca(PO4)2  +  10A1  +  3SiO2  =  3CaSiO3  +  5A13O3  +  3P3. 

When  a  mixture  of  calcium  metaphosphate  and  calcium 
sulphate  is  heated  with  aluminium,  a  violent  explosion 
ensues.  It  has  been  found  that  this  is  due  to  the  sulphate. 
Barium  sulphate  or  calcium  sulphate,  when  heated  with 
aluminium,  act  with  explosive  violence  and  sulphur  is  set 
free.  The  chlorides  are  also  decomposed  by  aluminium  at 
a  high  temperature.* 


PURE    PHOSPHORIC    ACID    FROM  SODIUM 
PHOSPHITE. 

H3P04. 

Crystals  of  hydrogen  sodium  phosphate  are  subjected 
to  the  action  of  gaseous  hydrogen  chloride.  In  this  man- 
ner syrupy  phosphoric  acid  in  amount  corresponding  with 
a  yield  of  75  per  cent,  of  the  theoretical  quantity  is 
obtained,  t 

Pure  phosphoric  acid  may  also  be  obtained  when  pow- 
dered calcium  phosphate  is  added  gradually  to  a  slight 
excess  of  commercial  hydrofluoric  acid  diluted  with  an 
equal  volume  of  water,  and  contained  in  a  leaden  or  plati- 
num vessel.  There  is  considerable  development  of  heat, 
and  the  liquid  must  be  thoroughly  agitated.  When  the 

*  A.  ROSSEL  and  L.  FRANK,  Her.  27,  52. 
|G.  WATSON,  J.  Soc.  Chem.  Ind.  2,  224. 

9 


I3O  LABORATORY    MANUAL    OF 

action  moderates,  the  liquid  is  gently  heated,  water  being 
added  to  make  up  for  loss  by  evaporation.  When  the 
liquid  becomes  viscous,  the  excess  of  hydrogen  fluoride 
begins  to  escape,  and  the  mixture  is  then  heated  until  the 
expulsion  of  the  acid  is  complete.  The  syrupy  liquid  thus 
obtained  contains  from  60  to  70  per  cent,  of  phosphoric  an- 
hydride in  the  form  of  orthophosphoric  acid.  With  pure 
materials,  the  phosphoric  acid  obtained  is  very  pure  ;  if 
bones  and  ordinary  acid  have  been  used  the  product  must 
be  heated  to  carbonize  the  organic  matter,  dissolved  in 
water,  filtered,  and  again  evaporated.  Pyrophosphoric  and 
metaphosphoric  acids  can  be  obtained  by  evaporating  at 
higher  temperatures.* 

Another  method  is  to  heat  127  grams  white  phosphor- 
us with  1400  c.  c.  nitric  acid  (1.20  sp.  gr.)  in  a  retort  with 
receiver.  The  phosphorus  me.Us,  and  then  the  operation 
quietly  proceeds.  At  intervals  the  distillate  must  be  poured 
back.  When  the  phosphorus  has  passed  entirely  into  solu- 
tion (after  10  to  12  hours)  it  is  evaporated  in  a  platinum 
dish  until  a  sample  taken  out  with  a  glass  rod  together  with 
cone,  sulphuric  acid  and  ferrous  sulphate  solution  ceases  to 
give  a  reaction  for  nitric  acid.  The  temperature  must  not 
exceed  188°  C.  The  acid  when  mixed  with  mercuric  chlor- 
ide solution  must  show  no  trace  of  phosphorus  acid.  After 
this,  it  is  treated  warm  with  sulphureted  hydrogen  until  on 
standing  there  is  no  further  precipitate  of  arsenic  sulphide, 
then  diluted  with  a  little  water,  filtered,  and  again  slowly 
evaporated,  until  a  thermometer  dipped  into  it  shows 
1 60  C. 


*  M.  NICOLAS,  Compt.  rend.,  in,  974. 


INORGANIC    PREPARATIONS.  131 

The  acid  should  show   a   sp.  gr.   of  1.88,  and  be  free 
from  arsenic  and  "phosphoric  acid. 


PHOSPHORUS    TRISULPHIDE. 


310  grams  red  phosphorus  are  mixed  with  480  grams 
powdered  sulphur  and  the  powder  poured  by  spoonfuls 
into  a  hessian  crucible  which  has  been  heated  on  a  Bunsen 
burner.  After  adding  each  portion,  the  crucible  is  closed 
with  a  cover  whereupon  the  reaction  should  take  place  at 
once.  When  the  whole  mixture  has  been  added,  the  cruci- 
ble is  allowed  to  cool  sufficiently  to  leave  the  mass  soft, 
and  then  the  phosphorus  sulphide  is  poured  out  on  a  piece 
of  sheet-iron.  The  solid  product  is  broken  in  pieces  while 
warm  and  placed  in  a  well-stoppered  bottle.  Phosphorus 
trisulphide  forms  in  a  hard,  gray,  easily  powdered  mass, 
which  when  exposed  to  air  becomes  moist  and  smeary,  de- 
veloping sulphureted  hydrogen. 


CALCIUM    PHOSPHIDE. 
CaP. 

To  a  strong  clay  crucible,  about  6^  cm.  wide  and  12 
cm.  high,  fit  a  round  cover  of  sheet-iron  2  mm.  thick  pro- 
vided with  a  round  opening  in  the  center  of  2.5  mm. 
diameter  and  into  which  is  fitted  an  iron  tube  30  cm.  long. 
At  the  upper  end  of  this  iron  tube,  a  thin  walled  glass 


132  LABORATORY    MANUAL    OF 

tube  of  1 5  cm.  in  length  is  fastened.*  Fig.  9.  After  having 
placed  the  iron  tube  perpendicularly  in  the  crucible,  the 
latter  is  filled  with  100  grams  burnt  marble  or  lime  in 
pieces  the  size  of  a  hazel  nut.  Cover  the  cruci- 
ble and  then  heat  in  Roessler's  annealing  furnace. 
When  the  crucible  has  become  red-hot,  65  grams 
of  dry  phosphorus  in  sticks  are  dropped  into  it 
through  the  glass  tube,  in  pieces  of  about  5  to  10 
grams.  Immediately  upon  dropping  each  piece 
of  phosphorus  the  glass  tube  is  closed  with  a 
cork  provided  with  a  handle.  The  influence  of 
phosphorus  on  the  lime  is  manifested  each  time 
by  the  escape  of  a  little  phosphorus  pentoxide 
in  form  of  a  white  cloud  of  smoke  from  the 
chimney  of  the  furnace.  If  this  reaction  fails 
to  take  place,  the  iron  tube  is  raised  a  little, 
allowing  the  phosphorus  to  enter  into  the  cruci- 
ble. While  at  first  only  minimum  quantities 
escape  reaction,  the  conclusion  of  the  operation 
is  shown  by  the  appearance  of  thick  smoke. 
The  flame  is  then  extinguished,  the  crucible  taken  out,  and 
the  product  immediately  upon  having  cooled  (still  slightly 
warm)  is  filled  into  a  well-closed  specimen  cylinder. 

7CaO  +  7P  =  Ca2P2O7  +  5CaP.  Calcium  phosphide 
forms  in  dark,  hard,  rainbow-colored  pieces,  which  when 
thrown  into  warm  water  develop  phosphureted  hydrogen : 
2CaP  +  4H2O  =  2Ca  (OH)2  -f-  PgH*.  \ 

*  For  this  purpose  wind  a  little  thin  asbestos  cord  around  the  glass  tube, 
then  twist  it  into  the  iron  tube,  after  having  moistened  the  asbestos  with 
water  glass.  The  joints  are  covered  with  a  pasty  mixture  of  powdered 
oxide  manganese  and  water  glass,  then  dried  at  moderate  heat.  The  glass 
tube  must  be  sufficiently  wide  to  conveniently  allow  the  passage  of  the 
phosphorus  sticks. 

f  GATTERMANN  and  HAUSSKNECHT,  Ber.  23,  1175. 


INORGANIC    PREPARATIONS.  133 


PHOSPHORUS  OXY  FLUORIDE. 

Zinc  carbonate  is  dissolved  in  excess  of  hydrofluoric 
acid,  the  solution  evaporated,  and  the  zinc  fluoride  dried 
at  300°  and  placed  in  a  brass  tube,  to  which  a  bromine 
burette,  containing  slight  excess  of  the  calculated  quantity 
of  phosphorus  oxychloride,  and  a  leaden  delivery  tube  are 
adapted  by  a  paraffined  cork.  The  leaden  tube  is  connected 
to  another  brass  tube  cooled  by  a  freezing  mixture  to  20°  C., 
and  this  leads  to  another  tube  containing  zinc  fluoride, 
which  removes  any  traces  of  oxychloride  escaping  from 
the  oxyfluoride.  The  phosphorus  oxychloride  is  dropped 
slowly  on  to  the  zinc  fluoride,  the  ensuing  reaction  being 
assisted  by  warming  carefully  at  40  to  50°  C.,  and  the 
evolved  gas  is  collected  over  mercury  in  glass  vessels.* 


HYDROGEN    PHOSPHIDE. 

PH3. 

Tin  and  zinc  phosphides  are  prepared  by  adding  the 
equivalent  quantity  of  amorphous  phosphorus  to  the  re- 
spective metals  in  the  molten  state  covered  with  ammo- 
nium carbonate.  Iron  phosphide,  FeP,  by  heating  finely 
divided  iron  and  amorphous  phosphorus  together,  copper 
phosphide,  by  heating  copper  filings  with  amorphous  phos- 
phorus ;  magnesium  phosphide,  by  adding  the  equivalent 
quantity  of  amorphous  phosphorus  to  melted  magnesium  ; 
sodium  phosphide  by  carefully  adding  yellow  phosphorus 


*  By  H.  MOISSAN,  Bull.  Soc.  Chim.  [3],  4,  260. 


134  LABORATORY    MANUAL    OF 

to  fused  sodium  under  petroleum.  The  phosphides  of  tin, 
zinc,  iron,  and  copper  are  not  decomposed  by  water ; 
whilst  those  of  sodium  and  magnesium,  like  that  of  calcium 
are  decomposed  by  water.  From  magnesium  phosphide, 
whether  decomposed  by  water  or  by  dilute  hydrochloric 
acid,  non-spontaneously  inflammable  hydrogen  phosphide 
is  obtained.  From  sodium  phosphide,  spontaneously  in- 
flammable hydrogen  phosphide  is  obtained,  which,  in  a 
great  measure,  readily  changes  to  solid  phosphide.  The 
phosphides  of  tin  and  zinc  are  decomposed  by  cold  dilute 
hydrochloric  or  sulphuric  acid,  but  those  of  iron  and  cop- 
per are  but  slightly  attacked  even  on  boiling. 

For  the  preparation  of  hydrogen  phosphide  from  the 
phosphides  of  tin,  zinc  or  magnesium,  an  Erlenmeyer  flask 
of  2OO  to  300  c.  c.  capacity  is  fitted  with  a  stopper  carrying 
three  tubes,  one  of  which  conducts  carbonic  anhydride  gas  to 
the  bottom  of  the  flask  to  displace  the  air,  the  second  ad- 
mits the  dilute  acid  from  a  tap-funnel,  the  third  is  the 
delivery  tube.  To  the  latter  is  attached  a  tube,  filled  with 
glass  wool,  from  which  the  gas  passes  out  into  nitric  acid 
in  a  dish.  In  the  case  of  tin  phosphide  the  flask  is  warmed 
gently  on  the  water-bath  at  the  commencement,  after  which 
the  reaction  proceeds  regularly  for  thirty  minutes  to  one 
hour,  .when  as  the  reaction  becomes  slower,  the  flask  may 
again  be  warmed.  In  the  case  of  zinc  or  magnesium  phos- 
phides, no  external  heating  is  requisite.  The  method  is 
preferable  to  the  preparation  with  potassium  hydroxide  and 
phosphorus  or  to  that  with  calcium  phosphide,  and  demon- 
strates the  formation  of  the  phosphide  of  hydrogen  in 
analogous  manner  to  the  other  compounds  of  hydrogen 
with  the  non-metals,  ammonia  excepted.  The  preparation 


INORGANIC    PREPARATIONS.  135 

of  zinc  phosphide  is  also  especially  recommended  as  being 
simple.  The  synthesis  of  hydrogen  phosphide  may  be 
shown  by  putting  sodium  phosphite  or  hypophosphite  into 
a  hydrogen  generator,  when  the  phosphide  is  readily  de- 
tected in  the  gas  evolved.* 


ARSENIC     ACID. 
H3AsO4. 

The  arsenic  acid  liquid  produced  in  preparing  nitrogen 
tetraoxide  (page  2  I )  is  poured  off  from  the  unchanged  pieces 
of  white  arsenic,  evaporated  to  dryness  in  a  porcelain  dish, 
and  the  residue  again  dissolved  by  heating  with  a  little 
water.  The  solution  must  be  free  from  arsenious  acid,  or 
else  must  be  again  evaporated,  adding  a  little  H2SO4,  and 
dissolved  once  more.  If  the  solution  is  pure  it  is  boiled 
down  to  a  syrup,  and  left  to  crystallize  at  a  low  tempera- 
ture in  a  closed  vessel,  adding,  if  necessary,  a  small  crystal 
of  arsenic  acid.  When  the  concentration  is  perfect,  very 
nice,  large,  compact  glossy  crystals  will  be  obtained;  if  the 
crystallization  has  occurred  too  quickly,  the  mass  is  dis- 
solved, the  crystals  are  melted  at  a  moderate  heat,  and 
then  allowed  to  slowly  crystallize,  so  that  larger  crystals 
may  be  obtained. 

Arsenic  acid  should  dissolve  readily  in  water,  and 
with  ferrous  sulphate  give  no  nitric  acid  reaction.  The 
well-diluted  solution  mixed  with  a  drop  of  HC1  should 
at  first  remain  clear ;  when  mixed  with  an  equal  volume 


*By  R.  LUEPKE,  Chem.  Centr.,  1890,  i  i,  642  ;  from  Zeit.  f.  physikal. 
und  chem.  Unterricht,  3,  280. 


136  LABORATORY   MANUAL   OF 

of  sulphureted  hydrogen  water  should  only  become  tur- 
bid upon  standing  some  time.  A  solution  of  the  acid 
in  fuming  HC1  should  immediately  give  a  thick  yellow 
precipitate  with  hydrogen  sulphide. 

2HNO3  +  As3O3  4-  2H3O  =  N3O3  +  2H3AsO4.  Arsenic 
acid  is  not  precipitated  from  aqueous  solution  by  hydrogen 
sulphide,  but  from  cone,  hydrochloric  acid  solution ;  it  is 
at  once  precipitated,  when  a  mixture  of  arsenic  pentasul- 
phide,  sulphur  and  arsenic  trisulphide  is  thrown  down.  In 
such  a  solution  arsenic  pentachloride,  which  is  unknown  in 
a  pure  condition,  seems  to  be  present,  and  this  is  decom- 
posed by  hydrogen  sulphide  according  to  the  equations : 

2AsCl5  4-  5H3S  =  As3S5  +  10HC1; 

AsCl5  4-  H3S  =  AsCl3  +  S  +  2HC1; 

2AsCl3  +  3H9S  =  As3So  +  6HC1. 


HYDROGEN    ARSENIDE. 

H  As. 

The  action  of  zinc  on  an  acid  solution  of  arsenious  acid 
produces  a  gas  containing  70  per  cent,  by  volume  of  hy- 
drogen arsenide.  Sodium  amalgam  containing  not  more 
than  4  grams  of  sodium  in  50  c.  c.  of  mercury,  by  its  action 
on  a  concentrated  solution  of  arsenious  acid,  produces  a 
gas  containing  86  per  cent,  by  volume  of  hydrogen  arsenide. 
A  gas  containing  a  large  quantity  of  arsenic  may  be  pre- 
pared by  the  action  of  aluminium  on  a  somewhat  dilute 
alkaline  solution  of  potassium  arsenite,  while  a  solution  of 
arsenic  disulphide  in  potash,  when  subjected  to  the  action 
of  aluminium,  evolves  a  gas  quite  free  from  arsenic.* 

*  A.  KAVAZZI,  Rend.  Ace.  Bologna,  1886-7,  85. 


INORGANIC  PREPARATIONS.  137 


ARSENIC     PENTASULPHIDE. 

As2  S5. 

When  a  solution  of  an  alkaline  arsenate,  strongly  acidi- 
fied with  hydrochloric  acid  and  saturated  with  hydrogen 
sulphide  is  heated  in  a  closed  vessel  at  100°  C.  for  one 
hour  the  arsenate  is  completely  converted  into  pentasul- 
phide.  It  contains  no  trisulphide,  and  if  due  precau- 
tions have  been  "taken  to  exclude  air,  no  free  sulphur. 
Pure  arsenic  pentasulphide  is  lemon  yellow  in  color, 
does  not  yield  any  sulphur  to  carbon  disulphide,  and 
dissolves  in  ammonia  without  separation  of  sulphur. 
When  the  ammoniacal  solution  is  agitated  with  silver  nitrate 
and  filtered  a  clear  filtrate  is  obtained,  from  which  nitric 
acid  precipitates  silver  arsenate.  Arsenical  pyrates  may 
oe  used  instead  of  alkaline  arsenate,  in  which  case  the 
finely  pulverized  ore  is  digested  for  some  time  in  aqua 
regia  until  decomposed  ;  the  chlorine  is  boiled  out  and  hy- 
drogen sulphide  passed  through  the  cold  solution  as  long 
as  a  precipitate  forms ;  this  serves  to  remove  heavy 
metals,  as  sulphides  ;  filter  and  wash  with  hydrogen  sul- 
phide water,  saturate  with  hydrogen  sulphide,  and  pro- 
ceed as  before.* 


ANTIMONY    TRICHLORIDE. 

SbCl3. 

IOO  grams  powdered  stibnite  arc  heated  with  500  c.  c. 
crude  HC1  in  a  flask,  gradually  adding  about  4  grams  po- 
tassium chloride.  When  the  ore  has  disappeared  filter  off 

*  L.  W.  McKAY,  Chem.  News,  54,  287. 


138  LABORATORY    MANUAL   OF 

from  the  sulphur  through  glasswool,  and  distill  out  of  the 
retort ;  at  first  aqueous  hydrochloric  acid  comes  over,  then 
a  concentrated  antimony  chloride  solution,  which  is  fre- 
quently of  a  yellow  color  from  iron  chloride,  finally  nice 
white,  pure  antimony  chloride,  cooling  in  crystals,  will  pass 
over.  Each  of  these  products  are  caught  up  separately. 
The  pure  antimony  chloride  is  refined  in  a  test  tube  or 
small  flask,  the  antimony  chloride  solution  decomposed  by 
a  large  quantity  of  water,  whereby  antimony  oxychloride 
is  precipitated  as  a  fine  white  powder  (Algaroth). 

The  change  Sb2S3  +  6HC1  ==  2SbCl3  4  3H2S  which  at 
first  goes  on  energetically,  but  gradually  becomes  very 
slow,  and  may  be  hastened  to  a  conclusion  by  adding  the 
means  of  oxydation. 

The  antimony  chloride  should  melt  at  73°  C.,  boil  at 
223°  C.,  and  crystallize  from  carbon  disulphide  in  rhombic, 
glossy  crystals. 


ANTIMONY     OXYCHLORIDE. 

Sb4O5Cl2. 

60  grams  powdered  antimony  sulphide  are  thoroughly 
mixed  in  a  mortar  with  140  grams  mercuric  chloride,  and 
slowly  distilled  from  a  gas  retort  over  the  gas  stove  at 
gentle  heat.  A  flask  is  used  as  receiver,  the  neck  of  which 
has  been  broken  off;  the  neck  of  the  retort  is  heated  at  in- 
tervals with  a  Bunsen  burner,  to  melt  the  antimony  chlo- 
ride that  solidifies  in  it.  The  distillate  is  dissolved  in  a 
little  warm  HC1,  and  then  poured  into  a  large  quantity  of 


INORGANIC    PREPARATIONS.  139 

hot  water ;  the   precipitate  is  washed   by   decantation  and 

then  dried. 

Sb2S3  4-  3HgCl2  =  2SbCl3  +  3HgS, 
4SbCl8  +  5H3O  =  Sb4O5Ci3  +  10HC1. 

The  white  crystalline  powder  should  be  insoluble  in 
water,  alcohol  and  ether,  but  soluble  in  carbon  disulphide 
and  chloroform.  On  heating  it  should  give  a  sublimate 
of  antimonious  chloride,  leaving  behind  antimony  mon- 
oxide.* 

ANTIMONIOUS     SULPHATE. 

Sb2(S04)3. 

20  grams  finely  powdered  antimony  are  added  to  400 
grams  of  boiling,  distilled  H3SO4  and  boiled  in  a  platinum 
dish  until  the  metal  has  disappeared.  A  part  of  the  sul- 
phate crystallizes  out  of  the  hot  solution,  the  rest  upon  the 
cooling  of  the  liquid,  in  the  form  of  small  white  needles.  It 
is  filtered  through  a  platinum  cone  and  dried  on  an  earthen 
plate. 

BISMUTH    NITRATE. 
Bi(N03)3  +  5H30. 

BASIC    BISMUTH    NITRATE. 
BiONO3  +  BiOOH. 

BISMUTH     HYDROXIDE. 
B  O  OH. 

100  grams  commercial  bismuth  and  50  grams  sodium 
nitrate  are  heated  in  a  nickel  dish  at  faint  red-heat.  After 


*  G.  E.  STAHL,  Zufallige  Gedanken  und  nutzliche  Bedanken  liber  den 
Streit  von  den  sogennaten  sulfure  Halle,  1715,  S.  346. 


140  LABORATORY    MANUAL    OF 

the  metal  is  completely  oxydized  boil  thoroughly  with  250 
c.  c.  water,  adding  a  solution  of  20  grams  sodium  hydrate 
in  1500.  c.  water.  The  bismuth  oxide  filtered  on  the 
bare  platinum  cone  is  dissolved  hot  in  a  flask  containing 
a  mixture  of  140  c.  c.  cone.  HNO3  with  200  c.  c.  water,  fil- 
tered through  an  asbestos  filter  and  evaporated  to  crystal- 
lization. The  mother  liquid  is  evaporated  further,  and 
poured  into  ^  litre  boiling  water,  whereupon  the  basic  bis- 
muth nitrate  separates  in  the  form  of  a  heavy  white  powder, 
which,  after  decanting,  is  collected  on  the  filter  and  dried 
in  the  cold ;  or  else  the  acid  solutions  are  precipitated 
with  ammonia,  the  bismuth  oxyhydrate  decanted  and  pre- 
served as  a  paste. 

The  impurities  of  commercial  bismuth  consist  chiefly 
of  arsenic  and  antimony,  the  oxides  of  which  go  into 
solution  upon  boiling  with  soda. 

The  bismuth  value  of  the  crystallized  nitrate  should 
be  ascertained  from  a  weighed  sample  by  converting  it 
into  bismuth  oxide  in  a  covered  porcelain  crucible,  heat- 
ing at  first  carefully,  then  energetically.  Further,  a  sample 
is  dissolved  in  very  dilute  nitric  acid,  the  solution  poured 
into  an  excess  of  hot  soda,  and  the  filtrate  tested  for  arsenic 
and  antimony. 


BISMUTH    IODIDE. 
BiI3. 

20  grams  iodine  are  mixed  with  35  grams  finely  pow- 
dered bismuth  in  a  mortar,  quickly  poured  into  a  retort, 
and  slowly  heated  on  the  gas  stove.  When  the  reaction 
is  finished  the  small  quantity  of  surplus  iodine  is  driven  out 


INORGANIC    PREPARATIONS.  14! 

by  a  current  of  dry  carbonic  acid  gas,  and  the  temperature 
raised  until  the  bismuth  iodide  sublimes  in  form  of  very 
large  crystals,  similar  in  appearance  to  iodine. 

Boiling  water   should    convert  the   powdered    bismuth 
iodide  into  red  oxyiodide. 

.S^»$&&    UBRxi/?p\ 

tTHIVEHSITY; 
c* 


BISMUTH    OXYI  O^^Ertt^ 
BiOI. 

95.4  grams  powdered  crystallized  bismuth  nitrate 
(page  139)  are  dissolved  in  120  to  160  c.  c.  glacial  acetic 
acid  by  warming  gently.  At  the  same  time  33.2  grams 
potassium  iodide  and  50  grams  crystallized  sodium  acetate 
are  dissolved  in  2  litres  cold  water.  The  second  solution 
is  placed  in  a  dish  and  the  first  added  to  it  in  a  very  thin 
stream  from  a  dropping  funnel,  with  frequent  stirring.  At 
the  point  where  the  liquid  strikes  a  greenish-black  pre- 
cipitate forms  at  first ;  upon  stirring  this  immediately 
changes  to  a  lemon  color.  On  further  addition  of  the 
bismuth  solution  the  product  assumes  a  dark,  brick-red 
color.  The  precipitate  settles  very  readily.  It  is  decanted, 
filtered  and  dried  at  IOO°  C. 

Bi(NO3)3  +  SKI  =  BiI3  +  3KNO3; 
Bi  I3  +  H2O  =  BiOI  f  2HI. 

The  hydriodic  acid  reacts  with  the  sodium  acetate, 
and  the  potassium  iodide  formed  again  takes  part  in  the 
reaction. 

Heated  in  a  dry  test-tube  the  compound  should  yield 
violet  iodine-vapors,  and  leave  behind  bismuth  oxide  ;  on 
shaking  with  water  no  halogen  acid  should  be  set  free, 


142  LABORATORY    MANUAL    OF 

and  it  should  be  free  from  arsenic  and  bismuth  subnitrate  : 
O.2  gram  shaken  with  2  grams  dilute  sulphuric  acid 
should  give  a  filtrate  which,  when  mixed  with  twice  its 
volume  of  cone.  H2SO4,  should  be  permanently  colored  blue 
by  a  drop  of  indigo  solution  (discoloration  nitric  acid).* 


BISMUTHIC     ACID. 
HBiO3. 

20  grams  of  bismuth  bromide  and  40  grams  of  potas- 
sium bromide  are  dissolved  in  60  grams  of  water  and 
mixed  with  excess  of  bromine.  The  solution  is  then 
poured  drop  by  drop  into  an  almost  boiling  solution  of  100 
grams  of  potassium  hydroxide  in  150  grams  of  water,  the 
alkali  remaining  in  excess  at  the  end  of  the  reaction.  A 
very  dense  red-brown  precipitate  forms  immediately.  This 
is  washed  repeatedly  with  boiling  water  by  decantation, 
and,  after  a  long  time,  part  of  the  product  forms  a  brown 
emulsion  with  the  water,  whilst  a  red-brown  compound 
remains  at  the  bottom  of  the  vessel.  The  emulsion  is  de- 
canted off,  and  can  be  precipitated  by  addition  of  a  few 
drops  of  nitric  acid.  The  non-emulsified  product  is 
washed  with  hot  water  until  no  longer  alkaline,  and  one 
portion  is  washed  for  several  days  longer.  Both  portions, 
when  dried  at  100°  C.,  have  the  composition  4KBiO3, 
3HBiO3.  The  same  product  is  obtained  from  bismuth 
chloride ;  k  dissolves  easily  in  hydrochloric  acid,  with 
evolution  of  chlorine,  but  is  soluble  only  with  difficulty  in 
warm  nitric  acid.  When  heated  it  becomes  pale-yellow, 


*  B.  FISCHER,  Die  neueren  Arzeneimittel,  III.  AufL,  s.  20. 


INORGANIC    PREPARATIONS.  143 

loses  oxygen,  then  becomes  brown,  melts,  and  on  cooling 
is  pale-yellow. 

Prolonged  washing  with  boiling  water  yields  a  product 
which,  after  being  dried  at  100°  C,  has  the  composition 
KBiO3,HBiO3. 

All  these  products  when  treated  with  warm,  dilute 
nitric  acid  lose  the  whole  of  their  potassium,  and  yield 
brick -red  bismuthic  acid,  HBiO3.  Very  often  the  residue 
dried  at  100°  C.  has  the  composition 


ANTIMONY  AND  BISMUTH  SULPHATES. 

Anhydrous  antimony  sulphate,  Sb2(SO4)3,  is  best  pre- 
pared by  dissolving  the  trisulphide  in  concentrated  sul- 
phuric acid  heated  to  the  temperature  at  which  it  com- 
mences to  vaporize ;  the  salt  is  deposited  as  a  fine,  very 
deliquescent,  white  crystallized  powder.  Its  products  of 
decomposition  with  water  vary  with  the  conditions,  such 
as  mass  and  temperature;  with  boiling  water  the  salt  is 
completely  decomposed  into  antimonious  oxide  (contain- 
ing less  than  I  per  cent,  of  water)  and  sulphuric  acid,  whilst 
with  water  at  ordinary  temperatures  a  basic  sulphate, 
5SB3O32SO37H3O,  is  produced.  The  sulphate  is  almost 
completely  converted  into  antimonious  chloride  by  a  cur- 
rent of  hydrogen  chloride.  Anhydrous  bismuth  sul- 
phate, Bi2(SO4)3,  prepared  in  a  manner  similar  to  the 
antimony  salt,  crystallizes  in  very  hygroscopic,  glis- 
tening needles  ;  when  evaporated  with  water  it  yields  a 

*  G.  ANDRE,  Compt.  Rend.,  113,  860-862. 


144  LABORATORY    MANUAL   OF 

slightly  coherent  powder  of  the  composition 
3H2O,  but  on  heating  it  with  water  at  the  ordinary  tem- 
perature, and  evaporating  the  solution,  a  powder  of  the 
composition  2Bi2(SO4)3  +  7H2O  is  obtained  ;  lastly,  if  the 
salt  be  frequently  treated  with  water,  the  final  product  is 
a  hydrate,  Bi2,O3,SO3,H2O.  It  is  probable  that  under 
favorable  conditions  the  sulphate  is  converted  by  hydro- 
chloric acid  into  bismuth  trichloride.* 


COBALT  NITRATE. 

Co(NO3)2,  Crystallized  +  5H2O. 

Fuse  in  a  Hessian  crucible  3  parts  of  potassium  disul- 
phate,  and  add  to  the  fused  mass,  in  small  portions  at  a 
time,  I  part  of  well-roasted  cobalt  ore  (the  purest  zaffre 
you  can  procure)  reduced  to  fine  powder.  The  mass 
thickens  and  acquires  a  pasty  consistency.  Heat  now 
more  strongly  until  it  has  become  more  fluid  again,  and 
continue  to  apply  heat  until  the  excess  of  sulphuric  acid  is 
completely  expelled,  and  the  mass  accordingly  no  longer 
emits  white  furties.  Remove  the  fused  mass  from  the 
crucible  with  an  iron  spoon  or  spatula  ;  let  it  cool  and 
reduce  it  to  powder;  boil  this  with  water  until  the  undis- 
solved  portion  presents  a  soft  mass  ;  then  filter  the  rose- 
red  solution,  which  is  free  from  arsenic  and  nickel  and 
mostly  also  from  iron.  Add  to  the  filtrate  a  small  quantity 
of  sodium  carbonate,  so  as  to  throw  down  a  little  cobalt 
carbonate  ;  boil  and  filter.  Precipitate  the  solution,  which 
is  now  free  from  iron,  boiling  with  sodium  carbonate;  wash 
the  precipitate  well,  and  treat  it  still  moist  with  oxalic 

*  C.  HENSGEN,  Rec.  Trav.  Chim.,  4,  401-413. 


INORGANIC    PREPARATIONS.  145 

acid  in  excess.  Wash  the  rose-red  cobalt  oxalate  thor- 
oughly, dry  and  heat  to  redness  in  a  glass  tube,  in  a  cur- 
rent of  hydrogen  gas.  This  decomposes  the  oxalate  into 
carbonic  acid  gas,  which  escapes,  and  metallic  cobalt,  which 
is  left  behind.  Wash  the  metal  first  with  water  containing 
acetic  acid,  then  with  pure  water;  dissolve  in  dilute  nitric 
acid,  treat,  if  necessary,  with  hydrogen  sulphide,  filter  the 
fluid  from  the  copper  sulphide,  etc.,  which  may  precipitate, 
evaporate  the  solution  in  the  water-bath  to  dryness. 

Solution  of  cobalt  nitrate  must  be  free  from  other 
metals,  and  especially  from  salts  of  the  alkali  metals ; 
when  precipitated  with  ammonium  sulphide  and  filtered, 
the  filtrate  must,  upon  evaporation  on  platinum,  leave  no 
fixed  residue. 


HYDROGEN    PEROXIDE. 

H3O3. 

One-half  litre  commercial  hydrogen  peroxide  is  cooled 
in  a  flask  to  o°  C.  and  mixed  with  a  cold,  saturated  barium 
hydrate  solution  until  a  permanent  precipitate  forms,  and  the 
solution  has  become  alkaline.  The  filtered  solution,  cooled 
and  shaken,  is  allowed  to  flow  into  2  litres  of  ice-cold 
barium  hydrate  solution.  When  the  crystalline  precipitate 
no  longer  forms,  the  peroxide  is  filtered  and  rinsed  with  a 
little  ice- water.  Now  20  c.  c.  cone.  H3SO4are  mixed  with  200 
c.  c,  water,  the  solution  carefully  cooled  in  a  freezing  mix- 
ture of  ice  and  common  salt,  and  enough  of  the  still  moist 
barium  peroxide  added,  shaking,  until  the  solution  reacts 
only  faintly  acid.  Then  it  is  allowed  to  settle ;  the  ice- 
cold  solution  is  filtered  and  neutralized  with  a  few  tlrops 


146  LABORATORY    MANUAL   OF 

of  dilute  barium  hydrate,  until  neither  H2SO4  nor  barium 
remains  in  the  solution.  Then  the  turbid  solution  is  fil- 
tered, and  a  part  of  the  thus  obtained  pure  hydrogen  per- 
oxide solution  evaporated  on  a  porcelain  plate  in  vacuum 
over  H2SO4. 

The  reactions:  H2O2  +  Ba(OH)3  =  Ba(OH)4  and 
Ba(OH)4  +  H3SO4  =  BaSO4  +  H2O2  will  only  take  place  in 
the  cold  and  in  not  too  high  concentration.  If  these  con- 
ditions are  not  fulfilled,  oxygen  developes  richly,  and  the 
gain  will  prove  a  minimum. 

The  anhydrous  peroxide  should  be  a  syrupy,  bitter- 
tasting  solution  of  1.46  sp.  gr.,  which  on  warming  decom- 
poses readily.  The  watery  solution  should  also  have  the 
peculiar  characteristic  taste  ;  and  yield,  when  mixed  with 
dil.  sulphuric  acid,  ether  and  a  drop  of  dilute  potassium 
dichromate  solution,  an  intense  blue,  ether-soluble  color ; 
be  free  from  HC1,H2SO4  and  barium.  One  per  cent,  of 
alcohol  is  added  for  preservation. 

The  value  is  determined  by  decomposing  I  c.  c.  hydro- 
gen peroxide  solution  with  excess  of  permanganate  of  potas- 
sium and  dil.  H2SO4  in  a  nitrometer,  or  else  by  titration 
of  5  c.  c.  with  Y£  normal  permanganate  in  sulphuric  acid 
solution.* 

Another  method  for  the  preparation  of  pure  hydrogen 
peroxide  is  to  take  the  solution  of  hydrogen  peroxide 
which  results  from  the  action  of  hydrochloric  acid  (sp.  gr. 
i.i)  on  barium  dioxide,  and  is  extracted  by  shaking  with 
ether;  the  ethereal  solution  is  agitated  with  distilled  water,  to 
which  it  yields  the  dissolved  hydrogen  peroxide.  By  repe- 
titions of  this  process,  a  pure,  neutral  solution  correspond- 

*  J.  THOMSEN,  Ber.  7-74. 


INORGANIC    PREPARATIONS.  147 

ing  with  O.8  to  0.9  per  cent  of  hydrogen  peroxide  is  obtain- 
able, from  which'  the  dissolved  ether  may  be  eliminated  by 
distillation  under  reduced  pressure.* 

It  can  also  be  prepared  by  adding  sodium  carbonate 
to  the  commercial  3  per  cent,  aqueous  solution  of  hydro- 
gen peroxide,  until  the  reaction  is  distinctly  alkaline.  The 
solution  is  then  filtered,  and  shaken  up  for  3  to  5  minutes 
with  10  to  12  times  its  volume  of  ether,  which  extracts 
about  half  of  the  hydrogen  peroxide  originally  present, 
and  leaves  behind  most  of  the  impurities.  The  ethereal 
layer  is  separated  and  reduced  to  o.Oi  to  0.0025  of  its 
original  volume  on  the  water-bath.  The  remainder  of 
ether  is  removed  in  a  bell  jar  by  solid  paraffin.  The  loss 
of  hydrogen  peroxide  during  the  evaporation  of  the  ether 
is  only  7  to  10  per  cent. 

Operating  in  this  way  two  solutions  are  obtained  :  (a) 
a  colorless  solution  with  distinctly  acid  reaction,  and  sp.  gr. 
1.1756,  which  contains  54  grams  of  anhydrous  hydro- 
gen peroxide  in  100  c.  c.;  (b]  a  thick  transparent 
slightly  yellow,  acid  liquid,  of  sp.  gr.  1.2475,  which  con- 
tains 79.6  grams  of  hydrogen  peroxide  in  100  c.  c.f 

Hydrogen  peroxide  chemically  pure  can  be  prepared 
by  mixing  hydrogen  peroxide  of  commerce  with  0.25  per 
cent,  of  phosphoric  acid  and  then  while  vigorously  stirring, 
barium  hydroxide  is  added  until  the  solution  is  neutral  to 
litmus.  The  clear  solution  is  poured  into  a  cold  saturated 
solution  of  barium  hydroxide  and  the  precipitate  of  barium 
dioxide  is  well  washed  and  may  be  kept  for  the  prepara- 
tion of  pure  hydrogen  dioxide.  For  this  purpose  it  is 


*  L.  CRISMER.  Bull.  Soc.,  Chim.  [3],  6,  24-25. 
\   P.  SHILOFF,  J.  Russ.  Chem.  Soc.,  25,  293. 


148  LABORATORY    MANUAL    OF 

made  into  a  thin  magma  and  carefully  decomposed  by 
dropping  steadily  into  dilute  sulphuric  acid  containing  12 
per  cent,  of  concentrated  acid  ;  and  excess  of  sulphuric 
acid  being  removed  by  hydroxide  and  vice  versa.  Excess 
of  barium  dioxide  must  be  avoided,  as  it  decomposes  hy- 
drogen dioxide.* 

POTASSIUM  AND  SODIUM  PEROXIDES. 

When  potassium  is  dropped  into  molten  potassium  ni- 
trate the  metal  burns  with  a  bright  light,  with  the  forma- 
tion of  yellowish  potassium  peroxide  which  dissolves  in  the 
fused  mass,  imparting  to  it  a  deep,  rich  red  color.  In  a 
similar  manner  sodium  and  sodium  nitrate  give  rise  to  a 
yellowish-red  solution,  whilst  potassium  and  potassium 
nitrate  give  a  brown-red  solution.  In  all  cases  the  color 
disappears  on  cooling,  but  on  heating  again  reappears.  The 
aqueous  solutions  from  the  colorless  masses  give  a  greenish 
precipitate  with  copper  sulphate.  The  action  of  sodium 
on  fused  potassium  chlorate  is  attended  with  dangerously 
explosive  violence.  t 

SULPHUR  MONOCHLORIDE, 


AND 

SULPHUR  DICHLORIDE, 
SClg. 

300  grams  sulphur  are  heated  to  its  melting  point  in  a 
tubulated  retort  over  a  low  flame,  and  as  in  the  case  of  tinte- 


*  Mann.  Chem.  Zeit.,  12,  857. 

f  H.  C.  BOLTON   Chem.  News,  53,  289-290. 


INORGANIC    PREPARATIONS.  149 

trachloride  a  rapid  stream  of  dry  chlorine  gas  is  passed 
close  to  the  surface  of  the  melted  sulphur.  The  vola- 
tile chloride  is  redistilled  in  a  side  neck  flask,  and  a 
little  dissolved  sulphur  remains  as  a  residue.  67.5  grams 
of  the  sulphur  monochloride  are  cooled  to  o°  C.  and 
saturated  with  dry  chlorine  gas.  The  sulphur  dichloride 
so  produced  must  weigh  103  grams.  It  is  preserved  in 
well-stoppered  bottles. 

In  the  redistillation  of  the  chloride  of  sulphur  the 
higher  chlorides  change  into  sulphur  monochloride;  on  the 
other  hand  at  o°  C.  sulphur  monochloride  combines  with 
another  molecule  of  chlorine  :  SgClg  +  Clg  =  2SC12. 

The  sulphur  monochloride  should  form  a  yellowish-red, 
strong-smelling  solution  of  1.7  sp.  gr.,  and  the  sulphur 
dichloride  a  dark  red  solution,  which  should  develop 
chlorine  at  ordinary  temperature  the  quantity  increasing 
with  the  temperature. 


PREPARATION  OF  CHROMIUM    FROM    POTAS- 
SIUM CHROMIUM  CHLORIDE    AND 
MAGNESIUM. 

Chromium  can  be  quickly  prepared  in  an  almost  chem- 
ically pure  condition  in  the  following  manner  :  Potassium 
dichromate  (100  grams)  is  dissolved  in  the  least  possible 
quantity  of  water,  the  solution  mixed  with  hydrochloric 
acid  of  sp.  gr.  1.124  (4°°  c-  c-)>  and  then  80  per  cent,  al- 
cohol (100  c.  c.)  gradually  added.  The  solution  of  potas- 
sium chromium  chloride  obtained  in  this  way  is  treated  with 
potassium  chloride  (160  grams),  the  filtered  solution  evap- 


150  LABORATORY    MANUAL    OF 

orated  to  dryness,  the  residue  heated  until  anhydrous,  freed 
from  the  green  portions,  which  are  produced  by  the  de- 
composition of  the  double  salt,  then  powdered,  and  mixed 
with  magnesium  filings  (50  grams).  This  mixture  is  heated, 
for  about  half  an  hour,  to  a  bright  red  heat,  in  a  closed 
Hessian  crucible  in  a  blast-furnace,  care  being  taken  that 
the  potassium  chloride  does  not  volatilize  completely, 
otherwise  the  chromium  is  partially  oxidized.  The  melt  is 
separated  from  the  superficial  layer  of  chromium  oxide, 
treated  with  water,  and  the  finely  divided  metal  freed  from 
salts  and  unchanged  magnesium  by  washing  it  with  water ; 
then  boiling  it  with  dilute  nitric  acid,  and  again  washing 
with  water,  all  the  washing  being  done  by  decantation. 
The  yield  of  the  metal,  dried  at  IOOQ  C,  is  about  27  grams. 
Chromium,  prepared  in  this  way,  is  a  light-gray,  crys 
talline,  non-magnetic  powder  of  sp.  gr.  6.7284  at  16°  C. 
it  can  be  melted  in  a  Deville's  furnace,  but  only  with  great 
difficulty,  and  after  being  melted  it  shows  a  silvery  fracture. 
Two  analyses  of  the  powder  showed  that  it  contained 
99-53  to  99. 5  7  per  cent  of  chromium,  and  that  it  was  free 
from  silver  and  magnesium.* 


CHROMYL    CHLORIDE. 
CrO2Cl3. 

200  grams  neutral  potassium  chromate  and  122  grams 
common  salt  are  melted  in  a  Hessian  crucible  at  a  moder- 
ate temperature,  the  fusion  is  poured  on  a  piece  of  sheet- 

*  E.  GLATZEL,   Ber.  23,  3127-3130. 


INORGANIC    PREPARATIONS.  151 

iron  and  broken  in  coarse  pieces,  these  are  digested  with  a 
mixture  of  66  c.  c.  fuming  H3SO4  (1.096  sp.  gr.)  and  134 
c.  c.  ordinary  cone,  HgSC^  in  a  roomy  retort  with  con- 
denser. The  reaction  is  very  violent  at  first  ;  when  it  mod- 
erates, the  retort  is  heated  until  no  more  brown  drops 
pass  over,  and  the  distillate  is  rectified  in  a  fractional  dis- 
tilling flask.  The  chromyl  chloride  is  preserved  in  sealed 
tubes. 

CrO3  +  2HC1—  H2O  = 


The  dark  red  oxychloride  which  fumes  when  exposed 
to  the  air  should  boil  at  I  i6Q  C. 


ANHYDROUS    CHROMIUM    CHLORIDE. 
CrCl3. 

The  chromium  oxide  obtained  as  per  directions  on 
page  151,  while  still  moist,  is  kneaded  to  a  paste  with  50 
grams  powdered  coal  and  thick  starch  paste.  Of  this,  bars 
are  formed  which  are  cut  in  pieces  of  2  to  3  cm.  long.  The 
pieces,  dried  at  a  moderate  heat,  are  packed  with  coal 
powder  in  a  Hessian  crucible,  covered  with  a  layer  of  coal 
powder,  closed  with  an  iron  cover  and  ignited  for  15 
minutes  in  Roessler's  furnace.  Now  a  porcelain  tube  is 
set  upright  in  a  Hessian  crucible,  the  crucible  filled  with 
the  pieces  of  chromium  oxide  mixture  which  have  been 
cooled  and  separated  from  the  surplus  coal-powder,  a  sec- 
ond crucible  of  the  same  size  with  perforated  bottom  is 
placed  upon  it  bottom  up.  A  short  glass  tube  passes 
through  a  small  hole  bored  in  the  side  of  the  upper  cruci- 


152 


LABORATORY    MANUAL   OF 


ble.  The  tubes  are  wound  with  a  little  asbestos  cord  and 
fit  tight  in  the  openings  ;  in  order  to  make  both  crucibles 
tight,  a  narrow,  thin  strip  of  soft  asbestos  board  is  wrapped 

around  the  joint  and  carefully  wound  with      k 

asbestos  cord,  finally  the  asbestos  cord  is 
saturated  with  water  glass  and  dried  at 
moderate  heat.  (See  fig.  10.)  Then  the 
crucibles  are  placed  in  a  Roessler's  anneal- 
ing furnace  and  this  covered  with  two 
semicircular  pieces  of  thick  sheet-iron 
which  have  an  opening  in  the  center 
through  which  the  upper  crucible  appears. 
It  is  first  heated  in  a  current  of  carbonic 
acid  until  no  trace  of  moisture  is  shown 
on  the  glass  tube.  Then  the  strongest 
heat  is  applied  and  it  is  ignited  in  a  cur- 
rent of  chlorine,  the  uncombined  chlorine 
passes  out  through  the  glass  tube  and  is 
absorbed  in  soda. 

Upon  cooling  the  chromium  chloride  is  found  sublimed 
in  the  upper  crucible  in  violet-red  very  glossy  scales  which 
are  insoluble  in  water. 

Cr3O3  +  3C  +  6C1  =  2CrCl8  +  SCO. 


FIG.  10. 


CHROMIUM    OXIDE. 
Cr3O3. 

250  grams  potassium  dichromate  are  thoroughly  mixed 
with  50  grams  of  sulphur  placed  in  a  clay  crucible  covered  and 


INORGANIC    PREPARATIONS.  153 

ignited  for  one  hour  in  Roessler's  annealing  furnace.  The 
green  contents  of  the  crucible  are  ground,  boiled  several 
times  with  water,  filtered  and  dried. 

K3Cr2Or  +  S  =  K3SO4+  Cr3O3. 

Only  traces  of  the  green  powder  should    go   into  solu- 
tion on  boiling  it  with  dilute  hydrochloric  acid. 


CHROMIUM    ACETATE. 
(CH3COO)2Cr. 

500  grams  fuming  HC1  are  poured  over  100  grams  po- 
tassium dichromate  in  a  flask,  and  the  chlorine  gas,  which 
develops,  upon  warming,  after  being  washed  with  water,  is 
used  in  the  preparation  of  chlorine  water  or  of  hypo- 
chlorite  of  sodium.  The  remaining  solution  is  evaporated 
to  a  very  small  volume,  poured  off  from  the  separated  po- 
tassium chloride  into  a  flask  with  300  grams  of  granulated 
zinc  and  rinsed  with  400  c.  c.  fuming  HC1.  The  flask,  in 
which  a  violent  evolution  of  hydrogen  should  take  place, 
is  closed  with  a  double-bored  rubber  stopper  similar  to 
that  of  a  wash  bottle.  As  soon  as  the  solution  has  as- 
sumed a  light  blue  color  similar  to  copper  sulphate  solution, 
the  glass  tube  permitting  the  free  passage  of  the  gas  is 
closed,  so  that  the  hydrogen  which  continues  to  develop 
vigorously  presses  the  solution  out  of  the  flask  through 
the  second  tube  which  reaches  to  the  bottom.  It  is  filtered 
through  a  small  bulb-tube  with  asbestos  and  then  enters 


154  LABORATORY    MANUAL   OF 

directly,  without  coming  in  contact  with  air,  into  a  solu- 
tion of  500  grams  crystallized  sodium  acetate  in  2  litres  of 
water.  The  red  precipitate  is  washed  by  decantation  sev- 
eral times  with  water  saturated  with  carbonic  acid  and  pre- 
served as  a  paste.* 

K2Cr2O7  +  14HC1  =2KC1  +  2CrCl3  +  6CI  +  7H2O; 
2CrCl3  -f  Zn  =  2CrCl2  -f  ZnCl2  ; 

CrClg  -f  2CH3COONa  =  2NaCl  +  CR8—  COO  >  Cr' 


The  reduction  of  the  chromium  chloride  only  takes  place 
rapidly  and  completely  in  concentrated  hydrochloric  acid 
solution  with  large  excess  of  zinc.  Chromium  monochloride 
absorbs  the  oxygen  of  the  air  with  great  rapidity,  while  the 
insoluble  chromium  acetate  is  fairly  stable  in  air. 

The  red  paste  should  form  a  blue  solution  with  diluted 
HC1,  and  by  energetic  absorption  of  oxygen  this  quickly 
turns  dark  green. 


POTASSIUM    CHLOROCHROMATE. 


IOO  grams  potassium  dichromate  ?re  powdered  and 
gently  heated  in  a  flask  with  a  mixture  of  100  c.  c.  of 
water  and  130  grams  pure  fuming  HC1.  As  soon  as  dis- 
solved, it  is  filtered  and  allowed  to  settle.  Next  day  the 


*  Pfordten  Annalen,  228,  113. 


INORGANIC    PREPARATIONS.  155 

crystals  are  separated  from  the  mother  liquor  by  decanta- 
tion  and  dried  on  an  earthen  plate. 

KO-C.O, 


0   , 
KG—  Cr02  -  KO—  CrO,,Cl 

The  large,  red  prisms  or  plates  develop  chlorine  gas  on 
heating  to  ioo°C. 


Of  TW 


SELENIUM. 

Se. 

Seleniferous  material  or  residues  are  melted  in  a  Hes- 
sian crucible  with  a  mixture  of  equal  parts  soda  and  salt- 
petre. The  cooled  fusion  is  boiled  up  with  water,  the  ex- 
tract condensed  to  small  volume,  and  the  solution,  which 
has  been  made  strongly  acid  with  cone,  hydrochloric  acid, 
is  boiled  with  a  reversed  condenser  until  no  more  chlo- 
rine gas  escapes.  Now  it  is  diluted  in  a  large  flask  with 
plenty  of  hot  water,  and  commercial  sodium  disulphite 
dropped  into  the  boiling  liquid  as  long  as  a  red,  very  vol- 
uminous precipitate,  which  quickly  clots  to  blackish,  ugly 
masses,  is  formed.  The  separated  selenium  is  settled,  col- 
lected on  a  filter  and  dried. 

In  fusing  with  soda  and  saltpetre  seleniferous  mate- 
rials produce  selenates  ;  selemc  acid  is  quickly  reduced 
in  cone,  solution  by  muriatic  acid  : 

H2SeO4  -f  2HC1  =  H2SeO3  +  2C1  +  H2O. 
Selenious  acid  is  decomposed  by  sulphurous  acid  : 
H2SeO3  +  2H2SO3  =  Se  +  2H2SO4  +  H2O. 

The  selenium  should  melt  at  217°  G.,  and  when  cooled 
slowly  crystallize  in  dark-gray,  metallic-shining  masses  ; 


156  LABORATORY   MANUAL   OF 

it  should  dissolve  in  cone,  sulphuric  acid,  with  a  green 
color,  and  be  reprecipitated  out  of  this  solution  by  water 
as  a  very  voluminous  red  armorphous  deposit.  Heated 
in  the  air  it  should  burn  to  selenium  dioxide  without  re- 
sidue, leaving  an  odor  of  radishes. 


HYDROFLUOSILICIC    ACID. 

H3SiF6. 

IOO  grams  calcium  fluoride  powder  are  mixed  with 
100  grams  dry  quartz-sand  (sea-sand),  and  carefully  heated 
with  350  c.  c.  cone,  sulphuric  acid.  The  escaping  gas  is 
led  through  an  empty  bottle  containing  a  safety-tube 
closed  with  a  little  cone,  sulphuric  acid,  and  then  into  a 
porcelain  dish,  at  the  bottom  of  which  a  small  vessel  with 
mercury  has  been  placed.  The  gas  tube  is  fastened  so 
that  it  dips  into  the  mercury,  and  then  400  c.  c.  distilled 
water  are  poured  over  it.  After  the  gas  evolution  has 
ceased,  the  silicic  acid,  which  has  separated  in  the  water, 
is  filtered,  washed  with  a  little  water,  until  the  combined 
filtrates  amount  to  400  c.  c.,  and  the  still  cloudy  acid  is 
filtered  through  a  folded  filter. 

By  the  water-absorbing  action  of  the  sulphuric  acid 
there  is  a  formation  of  silicon  fluoride  :  SiO2  -f  4HF— 2H2O 
=  SiF4;  this  gas  is  decomposed  by  water:  3SiF4  -j-4H2O 
=  2H2SiF6  +  Si(OH)4. 

The  acid  should  yield  a  precipitate  (Ba2SiO4)  with 
barium  chloride,  but  not  with  strontium  chloride,  in  hydro- 
chloric acid  solution.  To  determine  its  value,  the  acid 
is  titrated  with  soda  solution  to  alkaline  reaction.  The 


INORGANIC    PREPARATIONS.  157 

neutralization  of  the  acid  on  titration  with  soda  corresponds 
with  the  equation  :.  H2SiF6  +  GNaOH  =  6NaF  +-  Si(OH)4  f 
2H2O. 


PERCHLORIC    ACID. 
HC104. 

50  grams  potassium  perchlorate  are  distilled  out  of  a 
good-sized  retort  with  a  mixture  of  100  grams  cone. 
HaSO4  and  20  c.  c.  water.  The  distillate  is  freed  from  chlo- 
rine gas  by  gently  warming,  a  few  centigrammes  of  silver 
sulphate  and  barium  carbonate  added,  the  trifling  precipi- 
tates of  each  filtered  separately,  and  the  filtrate  redis- 
tilled. 

KC1O4  +  H2SO4=,  HC1O4  +  HKSO4. 

The  crude  acid  still  contains  traces  of  HC1  and  H3SO4, 
which  are  removed  in  the  manner  described. 

In  a  solution  of  potassium  chlorate  a  drop  of  the  acid 
produces  a  thick  crystalline  precipitate. 


MANGANESE. 
Mn. 

300  grams  crystallized  manganous  chloride  are  grad- 
ually dried  in  a  porcelain  dish  on  the  gas  stove, 
and  the  pieces  which  have  formed,  powdered  in  a  hot 
mortar  and  dried  until  the  pale  pink-colored  powder  fails 
to  clot  and  a  sample  heated  in  a  test-tube  shows  no  mois- 
ture. 75  grams  of  the  anhydrous  manganous  chloride  are 


158  LABORATORY    MANUAL    OF 

thoroughly  mixed  in  a  warm  condition  with  150  grams 
dry  potassium  chloride  (the  latter  must  first  be  heated 
in  a  nickel  or  iron  dish  until  it  no  longer  decrepitates),  and 
the  mixture  packed  tight  in  a  clay  crucible,  12  cm.  high 
and  7  cm.  wide.  The  crucible  is  covered  and  heated  in 
the  furnace.  When  the  crucible  has  become  red-hot  and 
the  contents  are  soft,  18  grams  magnesium  in  sticks  are 
thrown  in,  in  pieces  of  from  3  to  4  grams  each,  closing  the 
crucible  immediately  after  adding  each  piece  and  waiting 
for  the  faint  reaction.  The  real  difficulty  is  in  rapidly 
producing  the  exceedingly  high  temperature  in  the  fur- 
nace required  to  fuse  the  manganese  that  has  formed. 
This  can  be  accomplished  in  Roessler's  furnace  by  pro- 
viding a  very  good  gas  supply  and  by  introducing  a 
strong  oxygen  current  through  the  air-openings  on  the  side 
of  the  furnace.  (The  oxygen  is  generated  directly  from  a 
large  retort,  with  potassium  chlorate  and  a  little  black 
oxide  manganese,  which  is  heated  a  few  minutes  before 
adding  the  magnesium.  The  air-openings  of  the  furnace 
are  closed  loosely  with  strips  of  asbestos  board,  through 
which  the  gas-tubes  conveying  the  oxygen  pass.)  But  a 
well-built  brick,  air  or  blast  furnace,  with  coke  fire,  is 
preferable.  The  severe  heat  must  last  no  longer  than 
half  an  hour.  Upon  cooling,  if  the  operation  has  proved 
successful,  the  manganese  will  be  found  as  a  regulus.  If,  in 
place  of  this,  only  a  fine  black  metallic  powder  be 
found  which,  on  exposure  to  air,  changes  very  readily 
into  manganese  dioxide,  then  the  heat  was  too  low.  If, 
on  the  other  hand,  the  metal  has  solidified  in  crusts  and 
granules,  which  have  not  combined  to  a  regulus,  then  the 
crucible  contents  are  ground,  the  light  particles  quickly 


INORGANIC   PREPARATIONS.  159 

elutriated  with  a  large  quantity  of  water,  then  filtered, 
quickly  washed  with  alcohol  and  ether,  dried  between  fil- 
tered paper,  and  the  metallic  powder  so  obtained  is  pre- 
served in  well-closed  bottles. 

MnCl2  +  Mg  =  MgCl3  +  Mn. 

The  magnesium  chloride  volatilizes  and  reacts  with  the 
water-vapor  of  the  gases  of  combustion  to  form  hydrogen 
chloride  and  magnesium  oxide.  During  the  operation 
there  is  a  considerable  evolution  of  hydrochloric  acid  gas. 

Manganese  is  a  brittle,  glossy  metal,  when  exposed  to 
the  air,  especially  in  a  finely  divided  and  moist  condition,  is 
very  easily  oxidizable  and  when  excess  of  diluted  HC1  is 
poured  over  a  sample,  the  metal  should  dissolve  clearly 
with  a  vigorous  evolution  of  hydrogen.  The  solution 
prepared  hot  should  show  no  turbidity  with  excess  of 
ammonia,  or  at  most  a  hardly  noticeable  one.  When  am- 
monium sulphide  is  added  to  this  ammoniacal  solution,  a 
precipitate  of  flesh-colored  manganese  sulphide  forms, 
which  gradually  turns  green  on  boiling.  The  filtrate  from 
the  manganese  sulphide  mixed  with  sodium  phosphate 
gives  a  precipitate  of  magnesium  phosphate  which  is  never 
entirely  absent,  but  in  successful  working  should  be  very 
slight. 


MANGANESE    CHLORIDE. 

MnCl2  +  4H3O. 

Residues  of  chlorine  produced  from  black  oxide  of  man- 
ganese and  HC1  are  evaporated  to  dryness  in  a  porcelain 
dish,  and  the  residue  heated  for  a  time  on  the  gas  stove 
with  low  flame.  It  is  then  boiled  up  with  water  and  iVth 


160  LABORATORY    MANUAL    OF 

of  the  filtrate  precipitated  with  excess  of  soda  solution. 
The  precipitate  is  washed  with  water  decanting  several 
times,  then  the  main  quantity  is  added  to  the  solution  and 
digested  with  it,  warming  until  a  filtered  sample,  mixed 
with  ammonium  sulphide,  shows  a  pure  flesh-colored  pre- 
cipitate, which  on  dissolving  in  dil.  acetic  acid  leaves  no 
residue.  It  is  then  filtered  and  evaporated  to  crystalliza- 
tion. 

On  heating  the  dry  chlorides  and  boiling  with  water, 
the  compounds  of  the  trivalent  metals  (iron,  aluminium) 
decompose  with  formation  of  insoluble  basic  salts.  Pos- 
sibly the  rest  of  the  compound  is  precipitated  by  the 
manganese  carbonate 
3MnCO3  +  Fe2Cl6  +  3H2O  =  3MnCl2  +  Fe2(OH)6  +  3CO2. 

The  magnanese   chloride  is  tested  for  the  absence  of 
iron,  barium,  calcium  and  magnesium  salts. 


SOLUBLE  MANGANESE  OXIDE. 
4(MnO2H2O),Mn3O4. 

Obtained  by  acting  on  potassium  permanganate  with 
sodium  thiosulphate,  and  thoroughly  washing  the  precipi- 
tate with  water.  As  soon  as  all  the  potassium  has  been 
removed,  a  brown  solution  is  obtained,  from  which  the  oxide 
is  precipitated  on  the  addition  of  any  salt.  The  manga- 
nese solution  can  be  kept  for  a  long  time  in  sealed  tubes, 
but  if  filtered  through  paper  the  manganese  is  completely 
precipitated.* 


*  W.  SPRING  and  G.  DE  BOECK,  Bull.  Soc.  Chim.,  48,  170. 


INORGANIC    PREPARATIONS.  l6l 


MANGANOUS    SULPHIDE. 

MnS. 

Manganous  sulphide  is  thrown  down  from  ammoniacal 
manganous  solutions  by  ammonium  sulphide  as  a  pink 
precipitate,  which  the  older  workers  supposed  to  be  a  hy- 
drated  sulphide  ;  however,  it  is  shown  that  if  i'_  is  collected, 
washed  in  an  atmosphere  of  hydrogen  sulphide,  and  dried 
at  70°  C.  in  a  current  of  carbonic  anhydride  it  has  the 
composition  MnS.  The  sulphide  thus  obtained  consists 
of  tiny,  reddish,  transparent  crystals,  and  is  contaminated 
with  a  little  sulphur,  which  may  be  extracted  by  treat- 
ment with  carbon  bisulphide;  its  sp.  gr.  at  17°  C.  is  3.55. 

If  the  red  precipitate  be  well  washed,  and  left  in  a 
solution  of  ammonium  sulphide  for  a  few  days,  it  turns 
green  ;  the  same  change  is  also  brought  about  by  heating 
the  red  powder  at  300  to  320°  C.  The  green  modifica- 
tion is  crystalline,  and  has  the  same  composition  as  the 
red,  but  a  somewhat  higher  sp.  gr.,  namely,  3.63,  re- 
ferred to  water  at  17°  C.  Neither  modification  loses  sul- 
phur on  heating.* 


MANGANESE     SULPHATE. 
MnSO4,5H2O. 

A  concentrated  solution  of  MnSO4  is  treated  with  95 
per  cent  alcohol,  when  almost  all  of  the  sulphate  sepa- 
rates out  as  a  syrupy  liquid,  which  after  a  short  time 


*  By  U.  ANTONY  and  P.  DOMNINI.  Gazzetta,  23,  i.,  560-567. 


162  LABORATORY    MANUAL    OF 

begins  to  form  crystals.  If,  at  this  point,  the  liquid  and 
alcohol  be  repeatedly  and  strongly  shaken,  a  crystalline 
meal  results,  but  if  allowed  to  remain  at  rest,  well-formed, 
reddish  white,  prismatic  crystals  are  deposited.* 


POTASSIUM     MANGANATE. 

K2MnO4. 

Potassium  hydroxide  (2  mols)  is  placed  in  a  crucible, 
some  water  is  added,  and  finely  divided  potassium  per- 
manganate (2  mols)  is  added,  with  constant  stirring  and 
heating.  After  two  hours  at  a  faint  red  heat  the  crucible 
is  cooled,  and  the  manganate  placed  in  a  well-stoppered 
flask,  to  prevent  access  of  air  and  contact  with  organic 
matter,  t 

BARIUM    MANGANATE. 

BaMnO4. 

This  green  pigment  is  prepared  by  heating  manganese 
carbonate  with  2  to  2. 5  times  its  weight  of  commercial  barium 
dioxide  in  a  porcelain  crucible.  A  better  green  is  ob- 
tained when  well-pulverized  manganese  dioxide  (contain- 
ing 91  per  cent  of  MnO2)  is  heated  with  three  times  its 
weight  of  barium  dioxide.^ 


PREPARATION    OF  BARIUM  PERMANGANATE. 

BaMn3O8. 

Potassium  permanganate  (100  grams)  and  barium  ni- 
trate   (140  grams)  are  disolved  in  water  (i^  litres),  and 

*  B.  CLASSEN,  Arch.  Pharm.  [3]  25,  310. 

f  A.  JOLLER,  Rep.  Anal.  Chem.  1887,  No.  33. 

\  E.  DONATH,  Dingl.  Polyt.  Jr.  263,  246. 


INORGANIC    PREPARATIONS.  163 

to  the  boiling  solution  barium  hydroxide  is  added  in  por- 
tions of  20  grams,  until  no  further  evolution  of  oxygen 
takes  place.  The  whole  is  then  wanned  until  the  solu- 
tion has  become  colorless,  the  precipitate  of  barium  man- 
ganate  (containing  also  some  peroxide  and  carbonate)  is 
collected,  washed  5  times  by  decantation  with  5  litres  of 
boiling  water,  collected  on  the  filter-pump,  washed  10 
times  more  with  boiling  water,  suspended  in  water  (i  litre) 
and  carbonic  anhydride,  and  superheated  steam  passed  into 
the  mixture  for  10  hours.  The  solution  is  then  filtered 
twice  through  an  asbestos  filter  ;  it  contains  65  to  80  grams 
of  barium  permanganate.* 


FERRIC    CHLORIDE. 

Fe3Cl6. 

Heat  small  iron  nails  in  a  flask  with  a  mixture  of  10 
parts  of  water  and  one  part  of  pure  hydrochloric  acid  until  no 
further  evolution  of  hydrogen  is  observed,  even  after  add- 
ing the  nails  in  excess;  filter  the  solution  into  another  flask, 
and  conduct  into  it  chlorine  gas,  with  frequent  shaking  un- 
til the  fluid  no  longer  produces  a  blue  precipitate  in  a  solu- 
tion of  potassium  ferricyanide.  Heat  until  the  excess  of 
chlorine  is  expelled. 

Solutions  of  ferric  chloride  must  not  contain  an  excess  of 
acid  ;  this  may  be  readily  ascertained  by  stirring  a  diluted 
sample  with  a  glass  rod  dipped  in  ammonia,  when  the 
absence  of  any  excess  of  acid  will  be  proved  by  the  forma- 
tion of  a  precipitate  which  shaking  the  vessel  or  agitating 
the  fluid  fails  to  redissolve.  Potassium  ferricyanide  must 
not  impart  a  blue  color  to  it. 

*  By  F.  MUTHMANN,  Ber.  26,  1016-1018. 


164  LABORATORY    MANUAL   OF 


ANHYDROUS    FERROUS    CHLORIDE. 

FeCl2. 

Into  a  retort,  which  has  been  warmed  and  fitted  up  for 
the  production  of  ferric  chloride,  about  20  grams 
anhydrous  ferric  chloride  are  poured  as  quickly  as 
possible.  A  strong  current  of  carefully  dried  hydrogen 
gas,  developed  from  a  Kipp's  apparatus,  is  passed  over  it. 
The  retort  is  placed  on  a  gas  stove  which  may  be  lighted, 
when  it  is  certain  that  the  air  has  been  entirely  removed  from 
the  apparatus;  the  heat  should  be  moderate.  A  strong  evo- 
lution of  hydrogen  chloride  takes  place  at  once ;  the  gas 
is  collected  in  water.  When  the  chloride  in  the  retort  has 
changed  to  a  white  crystalline  mass  and  the  evolution  of 
HC1  ceases,  the  operation  is  concluded.  It  is  then  allowed 
to  cool  in  a  slow  current  of  hydrogen  ;  the  retort  is  broken 
while  still  warm  and  the  collected  chloride  preserved  in  the 
same  manner  as  the  ferric  chloride. 

Fe3Cl6  +  2H  =  2FeCl2  +  2HC1. 

Anhydrous  ferrous  chloride  forms  in  white  scales,  fairly 
stable  when  exposed  to  air,  melting  when  heated  vigorous- 
ly and  subliming  at  a  very  high  temperature. 


ANHYDROUS  FERRIC  CHLORIDE. 

Fe2Cl6. 

50  grams  bright  iron  wire  I  mm.  thick  in  pieces  6  to  8 
mm.  long  are  placed  in  a  tubulated  glass  retort  of  ^  litre 
capacity  and  strongly  heated  on  the  gas  stove,  a  chlorine  cur- 


INORGANIC    PREPARATIONS.  165 

rent,  dried  by  two  wash  bottles  with  sulphuric  acid,  is  led 
into  it  through  a  glass  tube,  which  passes  through  a  cork  in 
the  tubulature  of  the  retort  ending  just  above  the  iron. 
The  neck  of  the  retort  is  closed  with  a  bored  cork ;  the  es- 
caping chlorine  gas  is  either  led  out  through  a  rub- 
ber tube  or  else  absorbed  in  flasks  by  soda  or  alcohol. 
After  the  operation  has  lasted  I  to  2  hours,  the  gas  current 
and  heat  are  interrupted,  the  chlorine  which  fills  the  re- 
tort is  removed  by  dry  carbonic  acid,  the  retort  broken 
while  still  hot  over  a  large  sheet  of  smooth  paper,  and 
the  ferric  chloride  separated  from  the  broken  glass  and  un- 
changed iron,  from  which  it  is  very  easily  removed ;  it  is 
then  rapidly  placed  in  dry  and  warm  test  tubes  prepared  in 
readiness,  tared  and  fitted  with  suitable  stoppers  which  are 
immediately  closed  by  heating  before  the  blowpipe,  taking 
care  that  the  aqueous  products  of  combustion  do  not  enter 
the  tubes. 

The  ferric  chloride  formed  according  to  the  reaction: 
2Fe3-r6Cl  =  Fe3Cl6  escapes  the  reducing  influence  of  the  iron 
on  account  of  its  volatility  and  collects  in  beautiful  crystals 
in  the  upper  part  of  the  retort.*  The  process  is  only  suc- 
cessful with  complete  exclusion  of  moisture. 

Anhydrous  ferric  chloride  forms  dark  greenish,  compact 
scaly  masses,  with  a  beautiful  metallic  gloss,  dissolving 
quickly  in  brown  drops  when  exposed  to  the  air. 
Readily  dissolved  when  vigorously  warmed  in  water, 
alcohol  and  ether;  with  more  difficulty  in  benzol.  The 
solutions  are  colored  brown  and  react  acid. 


*  When  the  chlorine  current  is  too  sluggish  there  may  be  a  forma- 
tion of  ferrous  chloride,  which  then  remains  with  the  iron  as  a  fused 
white  mass. 


1 66  LABORATORY    MANUAL   OF 


FERROUS   SULPHATE. 
FeSO4,7H2O. 

Heat  an  excess  of  iron  nails  free  from  rust,  or  of  clean 
iron  wire,  with  dilute  sulphuric  acid  until  the  evolution  of 
hydrogen  ceases ;  filter  the  sufficiently  concentrated  solu- 
tion, add  a  few  drops  of  dilute  sulphuric  acid  to  the  filtrate 
and  allow  it  to  cool.  Wash  the  crystals  with  water  very 
slightly  acidulated  with  sulphuric  acid,  dry,  and  keep  for 
use. 

The  crystals  of  ferrous  sulphate  must  have  a  fine  pale 
green  color.  Crystals  that  have  been  more  or  less  oxidized 
by  the  action  of  the  air  and  give  a  brownish-yellow  solution 
when  mixed  with  water,  leaving  undissolved  ferric  sulphate 
behind,  may  be  treated  as  above,  with  sulphuric  acid  and 
excess  of  clean  iron  wire  or  nails,  until  the  residue  dissolves 
and  the  solution  is  clear  pale  green.  Hydrogen  sulphide 
must  not  precipitate  solution  of  ferrous  sulphate  after  ad- 
dition of  some  hydrochloric  acid,  nor  even  impart  a  black- 
ish tint  to  it. 


ANHYDROUS    FERROUS    BROMIDE. 
FeBr3. 

IOO  grams  of  bright  iron  wire  are  vigorously  heated  in  a 
round  bottom  flask  on  the  gas  stove,  and  100  c.  c.  bromine 
distilled  slowly  from  a  water-bath  into  the  flask.  The  glass 
tube  conducting  the  bromine-vapors  should  reach  close 
to  the  bottom  of  the  flask,  but  the  hot  glass  must  -be 
protected  from  fracture  by  the  dropping  bromine, 


INORGANIC    PREPARATIONS.  l6/ 

either  with  iron  filings  or  a  little  asbestos.  When  the  reac- 
tion begins  the  temperature  may  be  somewhat  moderated. 
Finally  dry  air  or  carbonic  acid  is  passed  through  the 
apparatus ;  upon  breaking  the  flask  the  preparation  is 
gathered  and  preserved  in  the  same  manner  as  described 
for  ferric  chloride. 


IRON    AMMONIUM    ALUM. 

Fe(NH4)(S04)2-f-12Aq. 

400  grams  ferrous  sulphate  are  dissolved  in  400  c.  c.  water 
70  grams  cone,  sulphuric  acid  and  about  120  grams  of  cone, 
nitric  acid  added  to  the  boiling  solution  until  a  diluted 
sample  mixed  with  ammonia  shows  a  pure  rust-colored  pre- 
cipitate. Now  it  is  evaporated  until  the  mass  is  resinous 
then  again  diluted  with  water  to  sp.  gr.  1.3 17  to  1.319.  To 
300  grams  of  this  ferric  sulphate  solution  a  solution  of  28 
grams  ammonium  sulphate  in  100  c.  c.  water  is  added  and  al- 
lowed to  cool  slowly  and  quietly.  The  crystals  are  washed 
with  a  little  cold  water  and  dried  without  warming. 

The  last  traces  of  nitric  acid  are  removed  from  the  fer- 
ric sulphate  solution  by  evaporation. 

Iron  alum  crystals  are  amethyst-colored  octahedra 
which  must  be  entirely  free  from  chlorine.  Determine  the 
iron  value  by  weighing  the  ferric  oxide  which  remains  after 
ignition  with  a  little  ammonium  nitrate. 


BERLIN    BLUE. 

Hydrocyanic  acid  residues  (page  124)  are  washed  with 
water  by  decantation  and  rinsed  in  a  porcelain  dish  with 


1 68  LABORATORY    MANUAL   OF 

crude  hydrochloric  acid.  A  chloride  of  lime  emulsion 
is  prepared  by  suspending  chloride  of  lime  in  water,  allow 
it  to  flow  in,  stirring  well,  through  a  funnel,  the  stem  of 
which  rests  on  the  bottom  of  the  dish  in  the  hydrochloric 
acid,  until  the  mass  has  turned  to  a  nice  blue  color  and  the 
solution  begins  to  smell  of  chlorine.  The  precipitate  is 
washed  with  a  dilute  solution  of  common  salt,  as  it  does 
not  settle  in  water. 

The  hydrocyanic  acid  residues  consist  of  the  ferro-salt 
of  hydrogen  ferrocyanide,  which  is  converted  into  ferric 
salt  by  the  oxidizing  influence  of  the  chloride  of  lime. 


PURE    PLATINUM. 

Pt. 

The  following  method  of  Finkener's  for  obtaining  plati- 
num free  from  impurities,  especially  iridium,  is  here  describ- 
ed; it  depends  on  recrystallization  of  sodium  platinochloride. 
Commercially  purified  platinum  is  dissolved  in  aqua  regia,  to 
the  solution  of  the  chloride,  freed  from  oxides  of  nitrogen, 
the  calculated  amount  of  pure  sodium  chloride  is  added,  the 
solution  is  concentrated  to  a  small  bulk,  and  allowed  to  cool 
whilst  being  continuously  stirred.  The  crystals  which  sep- 
arate are  freed  from  mother  liquor  by  suction,  washed  with 
a  concentrated  solution  of  sodium  chloride,  and  dissolved 
in  a  one  per  cent,  solution  of  sodium  carbonate.  The  solution 
is  allowed  to  cool,  when  the  salt  again  separates.  It  is 
then  dried  at  120°  C.,  reduced  in  a  current  of  hydrogen  at  a 
low  temperature,  and  the  platinum  sponge  thus  obtained  is 
washed  for  a  long  time  with  water,  and  finally  dried  and 
ignited.  The  metal  thus  obtained  is  extremely  pure ;  no 


INORGANIC    PREPARATIONS.  169 

impurities  could  be  detected  in  it  by  the  methods  mentioned 
above  and  it  is  calculated  that  it  contains  at  least  99.99  per 
cent,  of  platinum.* 

It  may  be  of  interest  to  mention  that  pure  platinum  is 
now  prepared  in  Germany.  The  method  of  purification  is 
simpler  than  the  English  one,  not  involving  the  use  of  lead, 
and  it  yields  a  very  pure  product.  In  a  sample  of  40  grams, 
no  palladium  or  rhodium  could  be  detected,  and  only  a 
trace  of  iridium;  a  trace  of  iron,  at  most  o.OOi  per  cent., 
was,  however,  present. 


PLATINIC     CHLORIDE. 

PtCl4,  Crystallized  j-10H2O. 

Heat  in  a  clay  crucible  5  parts  of  zinc  to  fusion,  with 
sufficient  common  salt  to  cover  the  surface  and  prevent  its 
oxidation,  then  introduce  I  part  of  platinum  scraps  in  small 
quantities  at  a  time  into  the  fused  metal.  An  alloy  is 
formed  from  which  the  zinc  is  to  be  removed  by  digesting 
in  somewhat  dilute  common  hydrochloric  acid,  until  all 
effervescence  ceases,  and  subsequent  boiling  for  a  time  with 
fresh  hydrochloric  acid.  The  residual  platinum  is  com- 
pletely washed  with  water  and  boiled  with  nitric  acid.  It 
is  again  washed,  and  finally  dissolved  by  warming  with  con- 
centrated hydrochloric  acid  and  some  nitric  acid.  Evapo- 
rate the  solution  on  the  water  bath,  with  addition  of  hydro-. 
chloric  acid,  and  dissolve  the  semifluid  residue  in  10  parts 
of  water  for  use. 


*  F.  MYLIERS  &  FOERSTER,  Ber.  25,  660  J^T  1  T 


I/O  LABORATORY    MANUAL   OF 

Platinic  chloride  must,  upon  evaporation  to  dryness  in 
the  water-bath,  leave  a  residue  which  dissolves  completely 
in  alcohol. 


PLATINIC    CHLORIDE. 

From   Residues, 

If  the  platinum  residues  contain  alkalies  and  organic 
substances  they  are  roasted  in  a  porcelain  dish  on  the  gas 
.stove,  then  mixed  with  a  little  diluted  crude  hydrochloric 
acid  and  reduced  by  zinc.  The  undissolved  zinc  is  removed, 
washed  and  the  impure  metal  boiled  up  several  times  with 
water  and  hydrochloric  acid.  The  residue  is  then  dissolved 
in  aqua  regia,  evaporated  to  a  small  volume  and  precipita- 
ted with  cone,  salammoniac  solution.  The  filtered  platinum 
ammonium  chloride  is  ignited  in  a  porcelain  crucible,  the 
residue  of  spongy  platinum  boiled  with  HC1,  dissolved  in 
aqua  regia,  and  evaporated  to  dryness  on  the  water-bath  in 
a  weighed  dish  occasionally  adding  a  few  drops  of  HC1. 
The  residue  of  pure  platinum  chloride  is  dissolved  in  10 
parts  of  water. 

Ten  drops  of  the  solution  with  one  drop  of  sodium  chlor- 
ide solution  evaporated  on  a  watch-glass  to  a  very  small 
volume,  should  on  cooling  yield  a  crystalline  mass,  in 
which,  under  the  microscope,  only  well  formed,  reddish-yel- 
low prisms  of  sodium  platinum  chloride  are  to  be  seen,  and 
which  must  not  be  contaminated  with  amorphous,  brown 
masses  (iron  ;  nitrogen  oxide  compounds  of  the  platinum 
chloride). 


INORGANIC    PREPARATIONS.  171 


PLATINOSOCHLORIDES. 

When  potassium  platinocbloride  (12  grams)  is  heated  in 
a  covered  vessel,  on  a  water-bath,  with  hydrogen  potassium 
sulphite  (9  grams)  and  water  (160  c.  c.)  for  10  to  12  hours, 
the  reduction  is  complete,  and  the  red  salt  crystallizes  out 
on  evaporation.  Similar  results  are  obtained  by  heating 
the  platinochloride  (9  grams)  with  potassium  hypophosphite 
(i  gram)  and  water  (300  c.  c.),  at  80  to  90°  C.,  for  1 8  to  20 
hours.  The  completion  of  the  action  is  shown  by  the  pure 
ruby  color  of  the  solution,  the  least  shade  of  orange  indica- 
ting the  presence  of  platinochloride.  The  first  method  is 
the  safest,  as  the  reduction  cannot  go  beyond  the  platino- 
sochloride,  but  in  the  second  method  the  red  salt  separates 
more  easily  and  completely,  and  with  care,  very  good  re- 
sults are  obtained.  If,  when  reducing  with  potassium  hy- 
pophosphite, the  action  is  continued  after  complete 
conversion  into  the  red  salt,  the  solution  rapidly  changes  to 
dark  brown.  Hydrochloric  acid  has  no  effect  on  this  so- 
lution, nitric  acid  discolorizes  it,  potash  causes  a  brown  pre- 
cipitate soluble  in  excess  of  the  precipitant,  and  ammonia  a 
brown  precipitate  insoluble  in  excess.* 


SPECIALLY  ACTIVE  PLATINUM-BLACK. 

Very  active  platinum-black  can  be  conveniently  pre- 
pared as  follows: — An  aqueous  solution  (50  to  60  c.  c.)  of 
platinic  chloride  (50  grams)  is  mixed  with  40  to  45  per 
cent,  of  formaldehyde  solution  (70  c.  c.),  the  mixture  cooled 


*  M.  CARY  LEA,  Amer.  Jr.  Sci.,  1894  [3],  48,397. 


LABORATORY   MANUAL   OF 

well,  and  then  sodium  hydroxide  (50  grams)  dissolved  in 
water  (50  grams)  gradually  added;  after  standing  for  12 
hours  the  solution  is  filtered.  A  yellow  liquid,  from  which 
a  small  quantity  of  platinum  is  deposited  on  boiling,  first 
passes  through  the  filter,  but  as  soon  as  most  of  the  salts 
have  been  washed  out  of  the  residue,  the  filtrate  assumes  a 
deep  black  color.  The  process  is  interrupted  at  this  stage 
for  several  hours  because  the  residue  soon  absorbs  oxygen, 
the  temperature  rising  to  36  to  40°  C,  and  the  washings  then 
pass  through  colorless.  As  soon  as  oxidation  is  complete, 
the  residue  is  washed  until  completely  free  from  sodium 
chloride,  pressed,  and  dried  over  sulphuric  acid. 

If  the  deep  black  filtrate  referred  to  above  is  submitted 
to  dialysis  in  absence  of  air,  a  black,  transparent  liquid  is 
obtained  which  is  stable  in  absence  of  air ;  on  exposure  to 
the  air,  however,  this  liquid  gradually  becomes  colorless, 
and  a  small  quantity  of  a  black  powder  is  deposited.  The 
black  solution  decomposes  hydrogen  peroxide  very  energet- 
ically, and  when  mixed  with  alcohol  or  shaken  with  air,  the 
odor  of  aldehyde  is  immediately  perceptible.  These  and 
other  experiments  seem  to  show  that  this  black  liquid  is 
a  solution  of  atomic  platinum  containing  small  quantities  of 
organic  platinum  compounds.*  , 


PENTATHIONIC    ACID. 

When  10  c.  c.  of  decinonnal  sodium  thiosulphate  solu- 
tion are  treated  with  a  drop  of  a  solution  of  potassium 
arsenite  containing  I  per  cent,  of  arsenic  trioxide,  and 


A.  LOEW,  Ber.,  23,  289. 


OF  THC. 


UNIVERSITY; 

r.       OF  ' 

INORGANIC    PREPARATIONS.  '  173 

with  an  excess  of  hydrochloric  acid,  the  solution  becomes 
turbid  and  has  a  slight  odor  of  hydrogen  sulphide ;  after  a 
long  time  arsenic  sulphide  and  a  little  sulphur  are  precipi- 
tated. When  filtered,  the  solution  gives  reactions  for  pen- 
tathionic  acid.* 


PREPARATION  OF  CRYSTALLIZED  HYDROXY- 

LAMINE. 

A  mixture  of  dry  hydroxylamine  zinc  chloride  (10 
grams)  and  anhydrous  aniline  (20  c.  c.)  is  distilled  under 
a  pressure  of  20  m.m.  on  a  water-bath.  The  distillate  of 
hydroxylamine,  which  crystallizes  on  cooling,  is  washed 
with  ether,  care  being  taken  to  prevent  access  of  moist  air; 
or  dry  ammonia  gas  is  passed  through  absolute  ether,  hold- 
ing the  zinc  salt  in  suspension,  and  the  decanted  etherial 
solution  of  hydroxylamine  is  subsequently  distilled  under 
reduced  pressure,  when  crystals  are  obtained. t 


HYDROXYLAMINE  HYDROCHLORIDE. 

A  saturated  solution  of  sodium  nitrite  (i  mol.)  is 
added  to  a  solution  of  hydrogen  sodium  sulphite  (2 
mols.)  in  a  cooled  vessel,  and  then  a  cold  saturated  solution 
of  potassium  chloride  is  added.  In  24  hours  hydroxyla- 
mine potassium  disulphonate  separates.  This  salt  is  boiled 
in  water  during  several  hours,  and,  on  cooling,  potassium 
sulphate  is  first  deposited,  and  subsequently  hydroxyla- 


*  T.  SALZER,  Ber.  19,  1696 

f    1..  CRISNER,  Bull.  Soc.  Chim.  [3],  6, 


174  LABORATORY    MANUAL   OF 

mine  sulphate.  A  solution  of  this  salt,  treated  with  the 
necessary  amount  of  barium  chloride,  yields  the  hydro- 
chloride,  which  can  be  obtained  in  colorless  crystals,  very 
hygroscopic,  easily  soluble  in  water  and  alcohol.  It  melts 
at  151°  C,  and  decomposes  at  a  higher  temperature, 
yielding  nitrogen,  hydrogen  chloride,  ammonium  chloride, 
and  water.* 


HYDRAZINE. 

Hydrazine  sulphate  is  best  obtained  when  triazoacetic 
acid  (250  grams  in  2  litres  of  water)  is  warmed  with  sul- 
phuric acid  (300  grams)  until  all  effervescence  ceases;  the 
sulphate  crystallizes  out  on  cooling.  More  may  be  ex- 
tracted from  the  mother  liquor  by  shaking  with  small 
quantities  of  benzaldehyde,  thus  converting  the  hydrazine 
into  benzalazine,  which  separates  out;  after  recrystalliza- 
tion  this  is  decomposed  by  sulphuric  acid,  whereby  hydra- 
zine sulphate  and  benzaldehyde  are  formed  ;  the  latter  is 
then  distilled  off.t 


CHYDRAZAINE      OR     PROTOXIDE     OF 
AMMONIA. 

Chydrazaine  is  evolved  when  a  solution  of  potassium 
permanganate  (158  grams)  and  sulphuric  acid  (40  grams  SO3) 
is  added  to  dried,  crystallized  ammonium  oxalate  (141.2 
grams)  thewhole  well  mixed  and  gently  heated  until  it  begins 

*  EICHKOFF,  Arch.  Pharm.  [3],  27,  713. 

f  T.  CURTIUS  and  R.  JAY,  Jr.  pr.  Chem.  [2],  39,27. 


INORGANIC    PREPARATIONS.  175 

to  boil.  The  gaseous  product  is  absorbed  in  hydrochloric 
acid,  and  a  neutral  solution  of  the  salt  can  thus  be  obtained. 
The  hydrochloride  is  crystalline,  and  very  readily  soluble 
in  water,  but  only  sparingly  in  alcohol.  The  sublimed 
salt  has  the  composition  N3H6O22HC1,  but  the  crystals 
dried  by  means  of  the  anhydrous  salt  contain  one-fifteenth 
of  their  weight  of  water.  When  a  solution  of  the  hydro- 
chloride  i.s  mixed  with  platinic  chloride,  a  platinochloride 
is  obtained,  the  composition  of  which  varies  with  the  con- 
ditions of  the  experiment ;  with  excess  of  the  hydro- 
chloride  a  yellow  salt  is  formed,  the  composition  of  which  is 
approximately  N3H6O,H3PtCl6,but  if  excess  of  platinic  chlo- 
ride is  added  the  proportion  of  platinum  is  sensibly  increased. 
The  sulphate  is  crystalline  and  soluble  in  water,  but  only 
sparingly  so  in  absolute  alcohol ;  it  forms  a  double-salt 
with  aluminium  sulphate.  The  nitrate  is  crystalline  When 
a  solution  of  the  nitrate  is  evaporated,  nitric  acid,  nitric 
peroxide,  nitrogen,  and  a  compound  having  the  composi- 
tion N2H2  are  evolved.* 


CARBON    OXYSULPHIDE. 

COS. 

Is  prepared  by  adding  50  c.  c.  of  a  concentrated  aque- 
ous solution  of  potassium  or  ammonium  thiocyanate  to  a 
cooled  mixture  of  290  c.  c.  (520  grams)  of  strong  sul- 
phuric acid  and  400  c.  c.  of  water.  The  whole  is  heated 
at  25°  C.  in  a  water  bath.  The  gas  thus  prepared  con- 
tains only  about  2.5  per  cent,  of  carbonic  anhydride  and 
0.05  per  cent,  of  carbon  disulphide.  The  latter  is  absorbed 


*  E.  J.  MAUMENE,  Bull.  Soc.  Chim.  49,  850. 


LABORATORY    MANUAL    OF 

by  passing  the  gas  through  triethylphosphine  and  this  in 
turn  is  removed  by  pure  sulphuric  acid.  Carbon  oxysul- 
phide is  only  absorbed  very  slowly  by  a  33  percent,  solu- 
tion of  potash.  If  the  gas  obtained  as  above  is  passed 
slowly  through  about  20  c.  c.  of  such  a  solution,  the  whole 
of  the  carbonic  anhydride  is  absorbed  with  a  loss  of  only 
about  7  per  cent,  of  the  oxysulphide.  A  33  per  cent, 
aqueous  solution  of  potash  mixed  with  its  own  volume  of 
alcohol  absorbs  carbon  oxysulphide  completely  and  rapidly, 
and  is  the  best  reagent  for  use  in  estimating  it. 

Pure  carbon  oxysulphide  is  odorless  and  tasteless.  Its 
physiological  effects  are  very  similar  to  those  of  nitrous 
oxide.  When  passed  through  a  saturated  solution  of 
baryta,  no  opalescence  is  produced  for  at  least  half  a  min- 
ute, while  if  any  carbonic  anhydride  is  present,  the  solu- 
tion becomes  milky  at  once.  With  lead  acetate  solution, 
the  precipitate  is  a  quarter  of  an  hour  in  forming.* 

NEW    METHOD    OF    PREPARING    CARBON    OXYSULPHIDE. 

Carbon  oxysulphide  is  obtained  when  carbonyl  chloride 
is  passed  through  concentrated  sulphuric  acid  to  dry  it, 
and  then  through  a  tube  50  cm.  long,  filled  with  ignited 
asbestos  well  mixed  with  finely  pulverized  cadmium  sul- 
phide, the  tube  being  placed  in  a  combustion  furnace  and 
heated.  Even  when  no  external  heat  is  applied  a  small 
quantity  of  carbonyl  sulphide  is  formed,  but  the  most 
favorable  temperature  for  its  formation  appears  to  be  260  to 
280°  C.  The  gas  thus  produced  is  found  on  analysis  to 
contain  COS,  94.87  per  cent ;  CO,  3.98  per  cent.;  air  1.15 
per  cent.  A  quantity  of  crystals,  which  are  identified  a;. 


*  P.  KLASON,  Jr.  pr.  Chem.  [2],  36,  64. 


INORGANIC    PREPARATIONS.  I  77 

cadmium  chloride,  are  observed  in  a  tube  previously 
charged  with  a  layer  of  cadmium  sulphide  and  heated  in  a 
flame  during  the  passage  of  a  current  of  carbonyl  chloride; 
the  reaction,  therefore,  appears  to  be  a  double  decompo- 
sition.* 


PURIFICATION  OF  CARBON  BISULPHIDE. 

To  one  litre  of  carbon  disulphide  0.5  c.  c.  bromine  is 
added  and  allowed  to  remain  for  3  to  4  hours.  The  bromine 
is  then  separated  again  by  shaking  the  carbon  disulphide 
with  a  slight  excess  of  potash  or  by  means  of  copper  turn- 
ings. The  carbon  disulphide  may  now  be  opalescent,  but 
this  is  readily  removed  by  agitating  it  with  a  little  potas- 
sium chloride,  when  the  filtered  disulphide  will  be  obtained 
clear,  colorless  and  of  agreeable  odor.  It  leaves  no  resi- 
due on  evaporation.! 


*  By  J.    NURICSAX,    Her.  24,  2967-2974. 
f   A.    CHENEVIER,  L'Union  pharm.,  33,  204 


1/8  LABORATORY    MANUAL    OF 

PREPARATION    OF    NORMAL    SOLUTIONS    OF 
ACIDS  AND  ALKALI. 

A  normal  solution  contains  in  one  litre  the  same  num- 
ber of  grams  of  the  substance  as  there  are  units  in  the 
molecular  weight.  Example  : 

Normal  HC1  36.5  gms.  per  litre. 

HNO3  63.0    " 

KOH  56.1     " 

NaOH  40.0    " 

N/HC1,  N/NHO3,  etc.,  are  the  expressions  usually  used. 
These  solutions  are  equivalent  as  shown  by  the  reaction, 

HC1  +  KOH  =  KC1  f  H2O 

36.5  +     56.1     =  74.6  +  "18 

The  same  is  true  of  NaOH  and  HNO3;  in  fact  all  compounds 
with  single  hydrogen  replacing  power  belong  to  this  class. 
Half  Normal  or  N/2  solutions,  as  of  H2  SO4  Na2  CO3,  etc., 
contain  one-half  of  the  molecular  weight  in  the  same  vol- 
ume; these  are  equivalent  to  the  first  class,  as  will  be  seen 
by  the  reaction, 

H2SO4  +  2KOH  =  K2SO4  +  H2O 

98  112   2  174-2  36 

or    49  56.1 

so  also  with  Na2CO3. 

It  is  impossible  to  weigh  out  any  exact  amount  of  a 
volatile  liquid  like  HC1  or  any  hygroscopic  solid  as  KOH, 
hence  we  must  prepare  these  solutions  indirectly.  The 
following  will  be  found  to  be  good  methods :  Take  pure 
dry  Na2CO3,  weigh  oft"  53  grams,  one-half  the  molecular 
weight,  and  dissolve  in  300  to  500  c.  c.  of  distilled  water,  cool 
to  15°  C.  and  dilute  to  exactly  one  litre;  now  make  up  a 
solution  of  H2SO4  a  little  more  than  half  normal  strength, 


INORGANIC    PREPARATIONS.  179 

using  the  hydrometer,  place  it  in  a  burette,  draw  10  c.  c.  of 
the  soda  solution  from  another  burette,  dilute  largely  with 
water,  add  a  few  drops  of  methyl  orange  (do  not  use 
phenolphthalein,  it  is  acid  to  CO2)  and  run  in  the  sulphuric 
acid  slowly,  stirring  vigorously  until  neutral.  Example  : 
IDC.  c.  NagCOs  require  9.8  c.c.  H2SO4 

Evidently  if  the  soda  solution  is  correct  the  acid  is  too 
strong  by  0.2  c.c.,  therefore  add  0.2  c.  c.  of  water  to  every 
10  c.  c.  of  the  solution  or  20  c.  c.  to  the  litre.  The  strength 
of  the  sulphuric  acid  may  also  be  determined  by  taking  any 
exact  quantity,  say  10  c.  c.,  adding  a  drop  or  two  of  HC1 
and  a  slight  excess  of  BaCl3,  weigh  the  BaSO4  and  calculate 
the  SO4  present ;  there  should  be  48  grams  per  litre.  In 
the  same  way  make  up  N/HC1;  the  strength  of  this  may  be 
determined  by  AgNO3,  either  volumetric  or  gravimetric.  In 
the  first  case  the  solution  must  be  neutralized  exactly  with 
KOH  or  NaOH  before  titration;  in  the  latter  made  slightly 
acid  with  HNO3.  The  normal  hydrochloric  acid  has  cer- 
tain advantages  over  sulphuric,  especially  in  organic  anal- 
ysis, as  the  sulphates  formed  during  the  reaction  are  more 
insoluble  in  organic  liquids,  alcohol,  etc.,  than  the  chlor- 
ides. 

An  acid  solution  may  also  be  prepared  by  using  oxalic 
acid  H3C3O4,  2H3O,  which  it  is  possible  to  obtain  in  a  state 
of  great  purity.  In  this  case  the  water  of  crystallization 
must  be  counted  in,  and  since  the  solution  is  N/2  or  half 
normal  we  need  63  grams.  The  strength  may  be  exactly 
determined  by  titration  with  K2Mn3O8  solution,  such  as  is 
used  for  iron  determinations  ;  the  solution  should  be  warm 
and  acid  with  sulphuric  acid  and  the  permanganate  added 
until  a  faint  pink  shade  is  obtained  5H3C3O4+K3Mn2O8 


i8o 


LABORATORY    MANUAL    OF 


4-  3H2SO4  =  10CO3  +  K2SO4  +  2MnSO4  +  8H3O.  Five 
parts  of  oxalic  acid  are  equal  to  10  parts  of  ferrous  iron. 

The  alkali  solutions  of  KOH  and  NaOH  are  made  up 
by  the  hydrometer  stronger  than  necessary,  cleared  of 
COg  by  the  addition  of  a  small  amount  of  BaCl2  and 
titrated  with  the  standard  acid  (if  it  be  H2SO4,  no  BaCl2 
must  be  used) ;  the  dilution  is  carried  out  the  same  as 
described  for  H2SO4. 

In  all  cases  the  acid  solutions  will  retain  their  strength 
much  longer  than  the  alkalies,  they  need  only  be  protected 
from  evaporation ;  with  the  alkali  the  case  is  different. 
CO2,  SO2,  H2S,  etc.,  are  absorbed,  glass  is  attacked,  hence 
the  strength  should  be  redetermined  from  time  to  time. 

Phenolphthalein,  acid  colorless,  alkaline  pink,  is  the 
best  indicator.  It  cannot  be  used  in  presence  of  ammo- 
nium salts  and  is  acid  to  CO2.  Methyl  orange  acid  pink, 
alkaline  yellow,  is  neutral  to  CO2  and  organic  acids,  and 
acts  in  the  presence  of  ammonium  salts. 


Table  of  equivalents  in  c.  c. 

HC1  0.0365 

HNO3  0.063 

H2SO4  0.049 

H2C2O4,  2H2O    0.063 

H3P04 

KOH 

NaOH 

NH4OH 

Na2CO3 

BaOH 


gram. 


INDEX. 


PAGE. 

id,  Arsenic.  .  .  .  '.  135 
'      Bismuthic    142 
Boracic  no   ' 

i' 
Antimony  Tritachloride   
Antimonious               
Arsenic  Pentasulphide  
"        Trioxide 

\GE. 

137 
139 
137 

22 

83 
84 
98 
96 

99 
35 
162 

97 
95 
98 
162 
98 
35 
167 

139 
140 

139 
139 
141 

143 
142 
no 
109 
107 
94 

63 
89 
89 
87 
9° 
36 
90 

131 

26 

29 
177 

28 

175 
10 

12 

H 
II 

'      Dithionic                         .         99 

Hydriodic  122   j 
Hydrobromic  118  \ 
'      Hydrochloric                    15,  16  ! 

Auric  Chloride 

Auroso  Auric  Chloride 

Barium  Carbonate  

Properties  of,     16 
Hydrocyanic  124  I 

"       Chloride  
Dithionate  
Hydroxide  

1      Hydrofluoric  125   ! 
'      Hydrofluosilicic  156  ! 
Hydrosulphuric  25 
'      Nitric                                        17 

'  '        Manganate 

"        Nitrate  
Oxide 

Properties  of  ig 
'      Perchloric               .        .    .  157 

"        Perhydrate  
"        Permanganate  
"        Peroxide  
Baryta  Water  
Berlin  Blue  
Bismuth  Hydroxide   41, 
Iodide    
"        Nitrate  

'      Pentathionic           .  .              172 

Phosphoric              .    .      .  .  129 

'      Silicic,  Crystalline  113 
Sulphuric  22 
"         Properties  of  .  .     24 
Icohol,  Commercial  5 

Ethyl  5 

"             "       Basic  
"        Oxyiodide 

luminium  Chloride  114,  115 
Anhydrous,  1  17 
Hydrate  n1", 
Oxide,  reduction  of,n6 
[urn,  Iron  Ammonium  167 
mmonia  .                   16,  30 

"        Sulphate    
Bismuthic  Acid 

Borasic  Acid  
Borax,  manufacture  of  
Boron  
Cadmium  Carbonate  
Caesium   Compounds,    Prepara- 
tion of 

"         Hydrate  30 
mmonium  P>icarbonate  67 
Bromide                        68 

Chloride  55 
'  '         Properties 
of  56 
Dichromate                   70 

Calcium  Carbonate    
"        Chloride     

"        porous  
"        Chromate  

Di  Hydrogen  Phos- 
phite        ..             72 

"        Hydroxide  
Phosphate,  crystalline. 
Phosphide  

Molybdate  54 
Nitrate                          71 

"        Sulphide 

Oxalate                         43 

Carbon  Dioxide 

Properties  of,  44 
"           Persulphate  .  .         .69 

"       Bisulphide  
"        Monoxide  
"        Oxysulphide  
Chlorine  

Protoxide                  .  1  74 

Sulphide  41 
'  '         Properties 
of  43 
mmonio  Zinc  Chlorides  72 
ntimony  Oxychloride  138 
"         Sulphate  .                  .  143 

"        Apparatus    for    a    con- 
stant supply  of  .... 
for      Laboratory     pur- 
poses 

"       from  Chloride  of  Lime. 

INDEX. 


Chlorine  Properties  of 14 

"         Water 10 

Chromium     149 

Acetate 153 

Chloride,  Anhydrous,  151 

Oxide 152 

Chromyl  Chloride 150 

Chydrazaine 1 74 

Cinnabar 104 

Cobalt  Nitrate   144 

Copper  Ammonium  Sulphate  .  .     75 
Potassium  .  .     75 

Cupric  Sulphate 76 

Cuprous  Ammonium  Iodide  ...     77 

"        Chloride 73 

"        Properties  of,     74 

"        Cyanide 74 

Oxide 76 

Phosphide    78 

Cuproammonium  Tetraiodide.  .     78 

Ferric  Chloride 163 

Anhydrous.  .  .  .  164 

Ferrous   Bromide,  Anhydrous..   166 

Chloride  .  .   i  64 

Sulphate    166 

Furnace,  Roessler's 37 

Cold 82 

"     Trichloride    83 

Hydrazaine 174 

Hydrofluosilicic  Acid 156 

Hydrogen g 

Arsenide 136 

Bromide 118 

Iodide 122 

Peroxide 145 

Phosphide 133 

Properties  of 10 

Sodium   Ammonium 

Phosphate  .     58 
"        Sulphite  ...     52 

Sulphide 25 

"        Arsenic 

fiee  from  .  .     26 
Propert  i  e  s 

of 27 

"         Hydrogen 
Arsenide,  free 

from 27 

Hydroxylamine 173 


Hydroxylamine  Hydrochloride.  173 

Iodine  Pentoxide 123 

"      Trichloride r24 

Iron  Ammonium  Alum 167 

Lead  Carbonate 39 

Dioxide 36 

"  "        Properties  of  ...     48 

"     Tetrachloride 40 

Lime 36 

Lithium  Normal  Arsenate 63 

"  "        Phosphate  ...     63 

Magnesium,  Basic  Carbonate.  .     87 
Carbonate,  crystal- 
lized, normal .  .     86 
Chloride  Anhydrous, 84 

Manganese 157 

Chloride 159 

"  Oxide TOO 

Sulphate 161 

Manganous  Sulphide 161 

Mercury 100 

Mercurous  Bromide 107 

Mercuric  Chloride 103 

"         Cyanide 104 

Mercurous  Iodide 106 

"  Nitrate 105 

Mercury,  Purification   of 102 

Mono  Calcium  Phosphate  Crys- 
talline       go 

"      Sodium  Phosphite 56 

Nitrogen.  . 10,   16 

Properties  of 10 

Tetraoxide 21 

Nitric   Oxide 20 

Nitrous    "     19 

Normal  Solutions 178 

Oxygen 7 

r'        Cubes 8 

"        Properties  of 8 

Phosphoric  Acid 129 

Phosphorus 128 

Phosphorus  Oxyfluoride 133 

Trisulphide 131 

Platinoso  Chlorides 171 

Platinum 1 68 

Black 171 

"  Platinic  Chloride.  ...  169 
Potassa,  Prepared  with  Baryta.  34 
Potassa,  Purified  with  Alcohol .  33 


INDEX. 


Ill 


PAGE.     ! 

Potassium  Bisulphate 58   : 

Bromide 68 

Chlorate 57 

Chlorochromate 154 

Cobaltic  Oxalate.  .  .       62 

Cyanate 60 

Cyanide 50 

Ferricyanide 59 

Hydroxide 31 

Iodide 60 

Manganate 162 

Metantimonate 62 

Nitrite 52,  53 

Properties    of,    53   I 

Peroxide 148 

Pyroantimonate 54 

Sulphide 43 

Sulphocyanide 51 

Koessler's   Furnace 37 

Rubidium  Compounds,  Prepar- 
ation of    63 

Salts,  Preparation  of,   64 

Selenium 155 

Silicon 1 10 

"      Chloride 113,   114,  115    ! 

Silver 79   i 

"     Potassium  Carbonate 81 

Sodium 46 

Acetate 44  : 

Amalgam 9,  47 

Ammonium      Hydrogen 

Phosphate 58 

Carbonate 48 

Free  from  Sul- 
phur     and 
Chlorine  .  .    48 
Free  from  Sil- 
ica      48 

Properties    of,  49 


Sodium  Chloride 45 

Dioxide 7 

Hydrogen  Sulphite 52 

"                "                 "         Prop- 
erties  of 52 

"       Hydroxide 31 

Specific  Grav- 
ity of    Solutions  of 33 

Nitrate 56 

"       Nitrite 53 

"       Peroxide 148 

Sulphide 43 

Stannic  Chloride,  Anhydrous..   127 

Stannous        "        126 

"       ,  Anhydrous  .  127 

Strontium  Hydroxide 92 

Salts,  Preparation  of,   93 

Sulphur  Dichloride 148 

Dioxide 27 

Properties     of,   28 

Monochloride 148 

Titanium  Trioxide 65 

Tungstates,  Free  from  Molybde- 
num       64 

Ultramarine 117 

Vanadyl  Chloride 67 

"        Trichloride 66 

Volumetric  Analysis 178 

Water i 

"       Ammonia  free 2 

Fiee  from  Organic    Mat- 
ter and  Ammonia. .  .       2 
Apparatus    for   Preparing 
free  from  Organic  Mat- 
ter and  Ammonia.  ...  3,  4 

,  Chlorine .     10 

Zinc  free  from  Arsenic 91 

"     Fisen 92 


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